Inhibitors of Tryptophan Dioxygenases (IDO1 and TDO) And Their Use In Therapy

ABSTRACT

Pharmaceutical compositions comprising 3-aminoisoxazolopyridine compounds of the Formula I having IDO1 and/or TDO inhibitory activity are described, where W is CR1, N or N-oxide; X is CR2, N or N-oxide; Y is CR3, N or N-oxide; Z is CR4, N or N-oxide; and at least one of W, X, Y, and Z is N or N-oxide; and R9 and R10 are as defined. Also described are methods of using such compounds in the treatment of various conditions, such as cancer.

TECHNICAL FIELD

The present invention relates to 3-aminoisoxazolopyridines, to pharmaceutical compositions containing them and their use as medicaments, and more particularly to their use in cancer therapy, either alone or in combination with other agents, such as anti-cancer vaccines, other types of immunomodulatory therapies, radiation and other chemotherapeutic agents.

BACKGROUND TO THE INVENTION

Indoleamine 2,3-dioxygenase 1 (IDO1) catalyses the first and rate limiting step of tryptophan conversion to kynurenine, and is expressed in a broad range of cancers to suppress the immune system (Uyttenhove et al., J. Nat. Med. 2003, 9, 1269). High IDO1 expression in clinical tumours has been shown to correlate with poor patient prognosis in a wide range of cancers including lung, colorectal, breast, melanoma and gynecologic cancers. Silencing of the IDO1 gene in a murine melanoma cell line resulted in reduced capacity of the cells to form tumours when implanted into mice (Zheng et al., J. Immunol. 2006, 177, 5639), validating IDO1 as a target for cancer intervention. A number of groups have pursued the development of small molecule inhibitors of IDO1 as an approach for restoring tumour immunity in cancer patients. Such inhibitors should have potential to exhibit antitumour activity on their own, or in combination with other standard chemotherapies. Blocking downstream signalling of the IDO1 enzyme with small molecule inhibitors also has the potential to synergise with other immunomodulatory approaches, such as anti-cancer vaccine administration, modulation of immune checkpoint proteins (such as CTLA4 and the PD1-4s) and the use of adoptive T-cell therapies (such as CART cells) (Mautina et al., Proceedings of the AACR Annual Meeting, 2014, Poster 5023). Early studies used derivatives of tryptophan such as 1-methyltryptophan (1-MT) as competitive inhibitors of IDO1 (Cady and Sono, Arch. Biochem. Biophys. 1991, 291, 326) and provided proof of concept that IDO1 would be an attractive target for pharmacological intervention of cancer (Hou et al., Cancer Res. 2007, 614). Natural products, isolated from marine invertebrates, inhibit IDO1 at considerably higher potencies than tryptophan derivatives. One of the most potent IDO1 inhibitors that has been described to date, with activity at nM concentrations, is an exiguamine isolated from a marine sponge (Brastianos et al., J. Am. Chem. Soc., 2006, 128, 16046). Two annulins isolated from marine hydroids exhibited activity at nM concentrations, and stimulated a medicinal chemistry program that generated a series of IDO1 inhibitory pyranonaphthoquinones with low nM potency (Pereira et al., J. Nat. Prod. 2006, 69, 1496; Kumar et al., J. Med. Chem. 2008, 51, 1706). High throughput screening of a compound library led to the discovery and optimisation of a structural class of hydroxyamidine inhibitors of IDO1 (Yue et al., J. Med. Chem. 2009, 52, 7364). An optimised hydroxyamidine candidate with nM potency against the enzyme in cells and with oral bioavailability is currently in clinical trials (Newton et al., J Clin Oncol. 2012, 30, (Suppl; abstract 2500)). Another potent IDO inhibitor of the imidazoisoindole class is also currently in early stage clinical trials (Mautina et al., Proceedings of the AACR Annual Meeting, 2013).

Tryptophan 2,3-dioxygenase (TDO) is another key enzyme in the tryptophan degradation pathway. TDO inhibitors may also have wide ranging therapeutic efficacy in the treatment of cancer and other conditions.

It is an object of the present invention to provide 3-aminoisoxazolopyridine compounds and their use in medicine, for example in cancer therapy, or at least to provide the public with a useful choice.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a pharmaceutical composition comprising:

a compound of Formula I or a pharmaceutically acceptable salt thereof, wherein:

W is CR², N or N-oxide;

X is CR², N or N-oxide;

Y is CR³, N or N-oxide;

Z is CR⁴, N or N-oxide;

and where at least one of W, X, Y, and Z is N or N-oxide;

R¹, R², R³ and R⁴ are each independently selected from the following groups: H, halo, R, —OH, —OR, —OC(O)H, —OC(O)R, —OC(O)NH₂, —OC(O)NHR, —OC(O)NRR, —OP(O)(OH)₂, —OP(O)(OR)₂, —NO₂, —NH₂, —NHR, —NRR, —NHC(O)H, —NHC(O)R, —NRC(O)R, —NHC(O)NH₂, —NHC(O)NRR, —NRC(O)NHR, —SH, —SR, —S(O)H, —S(O)R, —SO₂R, —SO₂NH₂, —SO₂NHR, —SO₂NRR, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —CN, —C≡CH, —C≡CR, —CH═CHR, —CH═CRR, —CR═CHR, —CR═CRR, —CO₂H, —CO₂R, —CHO, —C(O)R, —C(O)NH₂, —C(O)NHR, —C(O)NRR, —CONHSO₂H, —CONHSO₂R, —CONRSO₂R, cyclic C₃-C₇ alkylamino, imidazolyl, C₁-C₆ alkylpiperazinyl, morpholinyl and thiomorpholinyl;

or R¹ and R² taken together, or R² and R³ taken together, or R³ and R⁴ taken together can form a saturated or a partially saturated or a fully unsaturated 5- or 6-membered ring of carbon atoms optionally including 1 to 3 heteroatoms selected from O, N and S, and the ring is optionally substituted independently with 1 to 4 substituents selected from R;

each R is independently selected from any of the groups defined in paragraphs (a) and (b) below:

(a) an optionally substituted C₁₋₆ alkyl group, an optionally substituted C₂₋₆ alkenyl group, an optionally substituted C₂₋₆ alkynyl group and an optionally substituted C₃₋₇ cyclic alkyl group; wherein the one or more optional substituents for each of said alkyl, alkenyl, alkynyl and cyclic alkyl groups are each independently selected from the following groups: halo, —OH, —OR⁵, —OC(O)R⁵, —OC(O)NH₂, —OC(O)NHR⁵, —OC(O)NR⁵R⁵, —OP(O)(OH)₂, —OP(O)(OR⁵)₂, —NO₂, —NH₂, —NHR⁵, —NR⁵R⁵, —N⁺(O⁻)R⁵R⁵, —NHC(O)H, —NHC(O)R⁵, —NR⁵C(O)R⁵, —NHC(O)NH₂, —NHC(O)NR⁵R⁵, —NR⁵C(O)NHR⁵, —SH, —SR⁵, —S(O)H, —S(O)R⁵, —SO₂R⁵, —SO₂NH₂, —SO₂NHR⁵, —SO₂NR⁵R⁵, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —CN, —CO₂H, —CO₂R⁵, —CHO, —C(O)R⁵, —C(O)NH₂, —C(O)NHR⁵, —C(O)NR⁵R⁵, —CONHSO₂H, —C(O)NHSO₂R⁵, —C(O)NR⁵SO₂R⁵, cyclic C₃-C₇ alkylamino, imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl and azetidinyl; wherein each of the groups imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl and azetidinyl are optionally substituted by one or more of the following groups: C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cyclic alkyl, halo, —OH, —OR⁷, —OC(O)R⁷, —OC(O)NH₂—OC(O)NHR⁷, —OC(O)NR⁷R⁷, —OP(O)(OH)₂, —OP(O)(OR⁷)₂, —NO₂, —NH₂, —NHR⁷, —NR⁷R⁷, —N⁺(O⁻) R⁷R⁷, —NHC(O)H, —NHC(O)R⁷, —NR⁷C(O)R⁷, —NHC(O)NH₂, —NHC(O)NR⁷R⁷, —NR⁷C(O)NHR⁷, —SH, —SR⁷, —S(O)H, —S(O)R⁷, —SO₂R⁷, —SO₂NH₂, —SO₂NHR⁷, —SO₂NR⁷R⁷, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R⁷, —CHO, —C(O)R⁷, —C(O)NH₂, —C(O)NHR⁷, —C(O)NR⁷R⁷, —CONHSO₂H, —C(O)NHSO₂R⁷, —C(O)NR⁷SO₂R⁷, an optionally substituted aryl, and an optionally substituted heteroaryl group having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; and wherein the one or more optional substituents for each of said aryl and heteroaryl groups are each independently selected from the following groups: C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl or C₃₋₇ cyclic alkyl, halo, —OH, —OR⁸, —OC(O)R⁸, —OC(O)NH₂, —OC(O)NHR⁸, —OC(O)NR⁸R⁸, —OP(O)(OH)₂, —OP(O)(OR⁸)₂, —NO₂, —NH₂, —NHR⁸, —NR⁸R⁸, —N⁺(O)R⁸R⁸, —NHC(O)H, —NHC(O)R⁸, —NR⁸C(O)R⁸, —NHC(O)NH₂, —NHC(O)NR⁸R⁸, —NR⁸C(O)NHR⁸, —SH, —SR^(B), —S(O)H, —S(O)R⁸, —SO₂R⁸, —SO₂NH₂, —SO₂NHR⁸, —SO₂NR⁸R⁸, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R⁸, —CHO, —C(O)R⁸, —C(O)NH₂, —C(O)NHR⁸, —C(O)NR⁸R⁸, —CONHSO₂H, —C(O)NHSO₂R⁸, and —C(O)NR⁸SO₂R⁸; wherein each R⁵, R⁷ and R⁸ is independently selected from a C₁₋₆ alkyl group, a C₂₋₆ alkenyl group, a C₂₋₆ alkynyl group and a C₃₋₇ cyclic alkyl group; and

(b) an optionally substituted aryl, and an optionally substituted heteroaryl group having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; and wherein the one or more optional substituents are each independently selected from the same optional substituents as those defined in (a) above for R;

R⁹ and R¹⁰ are each independently selected from any of the groups defined in paragraphs (a) to (d) below, with the proviso that at least one of R⁹ and R¹⁰ is selected from any of the groups defined in paragraphs (c) and (d) below:

(a) H, an optionally substituted C₁₋₆ alkyl group, an optionally substituted C₂₋₆ alkenyl group, an optionally substituted C₂₋₆ alkynyl group, and an optionally substituted C₃₋₇ cyclic alkyl group; wherein the one or more optional substituents for each of said alkyl, alkenyl, alkynyl and cyclic alkyl are each independently selected from the following groups: halo, —OH, —OR¹¹, —OC(O)R¹¹, —OC(O)NH₂, —OC(O)NHR¹¹, —OC(O)NR¹¹R¹¹, —OP(O)(OH)₂, —OP(O)(OR¹¹)₂, —NO₂, —NH₂, —NHR¹¹, —NR¹¹R¹¹, —N⁺(O⁻)R¹¹R¹¹, —NHC(O)H, —NHC(O)R¹¹, —NR¹¹C(O)R¹¹, —NHC(O)NH₂, —NHC(O)NR¹¹R¹¹, —NR¹¹C(O)NHR¹¹, —SH, —SR¹¹, —S(O)H, —S(O)R¹¹, —SO₂R¹¹, —SO₂NH₂, —SO₂NHR¹¹, —SO₂NR¹¹R¹¹, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R¹¹, —CHO, —C(O)R¹¹, —C(O)NH₂, —C(O)NHR¹¹, —C(O)NR¹¹R¹¹, —CONHSO₂H, —C(O)NHSO₂R¹¹, —C(O)NR¹¹SO₂R¹¹, cyclic C₃-C₇ alkylamino, imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl, azetidinyl, aryl, and heteroaryl having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; wherein each of the groups cyclic C₃-C₇ alkylamino, imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl azetidinyl, aryl and heteroaryl are optionally substituted by one or more of the following groups: C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cyclic alkyl, halo, —OH, —OR¹³, —OC(O)R¹³, —OC(O)NH₂, —OC(O)NHR¹³, —OC(O)NR¹³R¹³, —OP(O)(OH)₂, —OP(O)(OR¹³)₂, —NO₂, —NH₂, —NHR¹³, —NR¹³R¹³, —N⁺(O⁻)R¹³R¹³, —NHC(O)H, —NHC(O)R¹³, —NR¹³C(O)R¹³, —NHC(O)NH₂, —NHC(O)NR¹³R¹³, —NR¹³C(O)NHR¹³, —SH, —SR¹³, —S(O)H, —S(O)R¹³, —SO₂R¹³, —SO₂NH₂, —SO₂NHR¹³, —SO₂NR¹³R¹³, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R¹³, —CHO, —C(O)R¹³, —C(O)NH₂, —C(O)NHR¹³, —C(O)NR¹³R¹³, —CONHSO₂H, —C(O)NHSO₂R¹³, and —C(O)NR¹³SO₂R¹³; wherein each R¹¹ and R¹³ is independently selected from a C₁₋₆ alkyl group, a C₂₋₆ alkenyl group, a C₂₋₆ alkynyl group and a C₃₋₇ cyclic alkyl group;

(b) an optionally substituted aryl, and an optionally substituted heteroaryl group having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; and wherein the one or more optional substituents for each of said aryl and heteroaryl are each independently selected from the same optional substituents as those defined in (a) above for R⁹ and R¹⁰;

(c) —C(O)R¹⁴, —C(O)OR¹⁴, —C(O)NR¹⁵R¹⁶, —C(O)SR¹⁴, —C(S)R¹⁴, —C(S)OR¹⁴ C(S)NR¹⁵R¹⁶, and —C(S)SR¹⁴, wherein each R¹⁴, R¹⁵ and R¹⁶ is independently selected from the group consisting of H, optionally substituted C₁₋₆ alkyl, optionally substituted C₂₋₆ alkenyl, optionally substituted C₂₋₆ alkynyl, optionally substituted C₃₋₇ cyclic alkyl, optionally substituted aryl, and optionally substituted heteroaryl having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S, and wherein the one or more optional substituents for each of said alkyl, alkenyl, alkynyl, cyclic alkyl, aryl and heteroaryl for R¹⁴, R¹⁵ and R¹⁶ are each independently selected from the same optional substituents as those defined in (a) above for R⁹ and R¹⁰; and

(d) —SO₂(CRR)_(n)R¹⁷, wherein n is an integer of from 0 to 6, each R is independently selected from the groups defined above for R, and R¹⁷ is optionally substituted aryl or optionally substituted heteroaryl having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S, and wherein the one or more optional substituents for each of said aryl and heteroaryl are independently selected from the same optional substituents as those defined in (a) above for R⁹ and R¹⁰; and —SO₂R¹⁸, wherein R¹⁸ is optionally substituted C₁₋₆alkyl or optionally substituted C₃₋₇ cyclic alkyl, wherein the one or more optional substituents for each of said alkyl and cyclic alkyl are each independently selected from those defined in (a) above for R⁹ and R¹⁰;

and a pharmaceutically acceptable carrier.

In another aspect, the invention provides a compound of Formula I, or a pharmaceutically acceptable salt thereof, for use as a medicament.

In another aspect, the invention provides a compound of Formula I, or a pharmaceutically acceptable salt thereof, for use in medicine.

In a further aspect, the invention provides a compound of Formula I, or a pharmaceutically acceptable salt thereof, for use as a therapeutically active substance.

In a further aspect, the invention provides a compound of Formula I, or a pharmaceutically acceptable salt thereof, for use in treating cancer in a warm blooded animal, including a human.

In a further aspect, the invention provides the use of a compound of Formula I, or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament.

In a further aspect, the invention provides the use of a compound of Formula I, or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for treating cancer in a warm blooded animal, including a human.

In a further aspect, the invention provides the use of a compound of Formula I, or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for treating cancer in a warm blooded animal, including a human, wherein the treatment comprises administration of the compound of Formula I and one or more additional agents selected from the group consisting of chemotherapeutic agents, immune-modulating agents such as anti-cancer vaccines, modulators of immune checkpoint proteins, adoptive T cell immunotherapies (for example chimeric antigen receptor T cells (CART cells)), and radiotherapy, and wherein the additional agent is administered either before, during or after administration of the compound of Formula I. In certain embodiments, the additional agent comprises an immune-modulating agent.

In a further aspect, the invention provides a method of treating cancer in a warm blooded animal, including a human, comprising administering to the animal a therapeutically effective amount of a compound of Formula I or a pharmaceutically acceptable salt thereof.

In a further aspect, the invention provides a method of treating cancer in a warm blooded animal, including a human, wherein the method comprises administering to the animal a therapeutically effective amount of a compound of Formula I or a pharmaceutically acceptable salt thereof, and wherein the method further includes the step of administering one or more additional agents selected from the group consisting of chemotherapeutic agents, immune-modulating agents such as anti-cancer vaccines, modulators of immune checkpoint proteins, adoptive T cell immunotherapies (for example chimeric antigen receptor T cells (CART cells)), and radiotherapy, and wherein the additional agent is administered either before, during or after administration of the compound of Formula I. In certain embodiments, the additional agent comprises an immune-modulating agent.

In a further aspect, the invention provides a method of inhibiting indoleamine 2,3-dioxygenase 1 (IDO1) in a warm blooded animal in need thereof, including a human, comprising administering to the animal a compound of Formula I or a pharmaceutically acceptable salt thereof having IDO1 inhibitory activity, in an amount effective to inhibit IDO1.

In a further aspect, the invention provides a method of inhibiting tryptophan2,3-dioxygenase (TDO) in a warm blooded animal in need thereof, including a human, comprising administering to the animal a compound of Formula I or a pharmaceutically acceptable salt thereof, having TDO inhibitory activity, in an amount effective to inhibit TDO.

In a further aspect, the invention provides a method of inhibiting IDO1 and TDO in a warm blooded animal in need thereof, including a human, comprising administering to the animal a compound of Formula I or a pharmaceutically acceptable salt thereof having both IDO1 and TDO inhibitory activity, in an amount effective to inhibit IDO1 and TDO.

In a further aspect, the invention provides a pharmaceutical combination or kit, comprising

-   -   (a) a compound of Formula I or a pharmaceutically acceptable         salt thereof, and     -   (b) one or more additional agents selected from the group         consisting of chemotherapeutic agents, and immune-modulating         agents such as anti-cancer vaccines, modulators of immune         checkpoint proteins and adoptive T cell immunotherapies (for         example chimeric antigen receptor T cells (CART cells)).

In a further aspect, the invention provides a pharmaceutical combination or kit, for use in treating cancer, comprising

-   -   (a) a compound of Formula I or a pharmaceutically acceptable         salt thereof, and     -   (b) one or more additional agents selected from the group         consisting of chemotherapeutic agents, and immune-modulating         agents such as anti-cancer vaccines, modulators of immune         checkpoint proteins and adoptive T cell immunotherapies (for         example chimeric antigen receptor T cells (CART cells)).

In a further aspect, the invention provides a compound of Formula I, or a pharmaceutically acceptable salt thereof, for use in treating a condition or disorder selected from the group consisting of: an inflammatory condition, an infectious disease, a central nervous system disease or disorder, coronary heart disease, chronic renal failure, post anaesthesia cognitive dysfunction, a condition or disorder relating to female reproductive health, and cataracts.

In a further aspect, the invention provides the use of a compound of Formula I, or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for treating a condition or disorder selected from the group consisting of: an inflammatory condition, an infectious disease, a central nervous system disease or disorder, coronary heart disease, chronic renal failure, post anaesthesia cognitive dysfunction, a condition or disorder relating to female reproductive health, and cataracts.

In a further aspect, the invention provides a method of treating a condition or disorder selected from the group consisting of: an inflammatory condition, an infectious disease, a central nervous system disease or disorder, coronary heart disease, chronic renal failure, post anaesthesia cognitive dysfunction, a condition or disorder relating to female reproductive health, and cataracts, in a warm blooded animal, including a human, wherein the method comprises administering to the animal a therapeutically effective amount of a compound of Formula I or a pharmaceutically acceptable salt thereof.

Certain embodiments of compounds of Formula I, that may be used in any of the compositions, methods, uses and other aspects of the invention as defined above, are described in the numbered paragraphs (1) to (30) below.

-   -   (1). A compound of Formula I or a pharmaceutically acceptable         salt thereof, as defined above in the first aspect of the         invention.     -   (2). A compound as defined in paragraph (1), wherein Z is N or         N-oxide, such as N, W is CR¹, X is CR² and Y is CR³.     -   (3). A compound as defined in paragraph (1), wherein X is N or         N-oxide, such as N, W is CR¹, Y is CR³ and Z is CR⁴.     -   (4). A compound as defined in paragraph (1), wherein X and Z are         both N or N-oxide, such as N, W is CR¹ and Y is CR³.     -   (5). A compound as defined in any one of paragraphs (1) to (4),         wherein R¹, R², R³ and R⁴, where present, are each independently         selected from the group consisting of H, halo, optionally         substituted C₁-C₆ alkyl, —O—R wherein R is optionally         substituted C₁-C₆ alkyl, an optionally substituted aryl, such as         substituted phenyl, and an optionally substituted heteroaryl         group having up to 12 carbon atoms and having one or more         heteroatoms in its ring system which are each independently         selected from O, N and S.     -   (6). A compound as defined in any one of paragraphs (1) to (4),         wherein R¹, R², R³ and R⁴, where present, are each independently         selected from the group consisting of H, halo, optionally         substituted C₁-C₆ alkyl, —O—R wherein R is selected from         optionally substituted C₁-C₆ alkyl and optionally substituted         aryl (such as phenyl), —NHR wherein R is optionally substituted         aryl, an optionally substituted aryl, and an optionally         substituted heteroaryl group having up to 12 carbon atoms and         having one or more heteroatoms in its ring system which are each         independently selected from O, N and S.     -   (7). A compound as defined in paragraph (6), wherein R¹, R², R³         and R⁴, where present, are each independently selected from the         group consisting of H, halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆         alkyl, such as methyl, substituted aryl, substituted heteroaryl,         —OR wherein R is optionally substituted aryl, and —NHR wherein R         is optionally substituted aryl.     -   (8). A compound as defined in paragraph (6), wherein one or two         of R¹, R², R³ and R⁴, where present, is H, and the others of R¹,         R² R³ and R⁴ that are not H are independently selected from the         group consisting of halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆         alkyl, such as methyl, substituted aryl, substituted heteroaryl,         —OR wherein R is optionally substituted aryl, and —NHR wherein R         is optionally substituted aryl.     -   (9). A compound as defined in any one of paragraphs (6) to (8),         wherein R³ is present and selected from the group consisting of         halogen, —OR wherein R is optionally substituted aryl, and —NHR         wherein R is optionally substituted aryl.     -   (10). A compound as defined in paragraph (2), wherein Z is N or         N-oxide, such as N, W is CR¹, X is CR² and Y is CR³, and R³ is         selected from the group consisting of halogen, —O—R wherein R is         optionally substituted aryl, and —NHR wherein R is optionally         substituted aryl.     -   (11). A compound as defined in paragraph (2), wherein Z is N or         N-oxide, such as N, W is CR¹, X is CR² and Y is CR³, R¹ is H,         and one or both of R² and R³ are other than H, for example, both         R² and R³ are other than H, or R² is H and R³ is other than H,         or R³ is H and R² is other than H.     -   (12). A compound as defined in paragraph (11), wherein each of         R² and R³ that is other than H is independently selected from         the group consisting of halogen, optionally substituted C₁-C₆         alkyl, —OR wherein R is selected from optionally substituted         C₁-C₆ alkyl and optionally substituted aryl, —NHR wherein R is         optionally substituted aryl; an optionally substituted aryl,         such as substituted phenyl, and an optionally substituted         heteroaryl group.     -   (13). A compound as defined in paragraph (12), wherein each of         R² and R³ that is other than H is independently selected from         the group consisting of halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂,         C₁₋₆ alkyl such as methyl, substituted aryl, substituted         heteroaryl, —OR wherein R is optionally substituted aryl, and         —NHR wherein R is optionally substituted aryl.     -   (14). A compound as defined in any one of paragraphs (1) to (4),         wherein R¹ and R² taken together, or R² and R³ taken together,         or R³ and R⁴ taken together form a saturated or a partially         saturated or a fully unsaturated 5- or 6-membered ring of carbon         atoms optionally including 1 to 3 heteroatoms selected from O, N         or S and the ring is optionally substituted with 1 to 4         substituents independently selected from R, and those of R¹, R²,         R³ and R⁴ that are not part of the ring, are independently         selected from: H, halo, optionally substituted C₁-C₆ alkyl, O—R         wherein R is optionally substituted C₁-C₆ alkyl, an optionally         substituted aryl and an optionally substituted heteroaryl group         having up to 12 carbon atoms and having one or more heteroatoms         in its ring system which are each independently selected from O,         N and S.     -   (15). A compound as defined in any one of paragraphs (1) to         (14), wherein one of R⁹ and R¹⁰ is selected from the group         consisting of H and optionally substituted C₁₋₆ alkyl (such as         C₁₋₃ alkyl), for example, one of R⁹ and R¹⁰ is H, and the other         of R⁹ and R¹⁰ is selected from any of the groups defined in (c)         and (d).     -   (16). A compound as defined in any one of paragraphs (1) to         (15), wherein one of R⁹ and R¹⁰ is selected from the group         consisting of H and optionally substituted C₁₋₆ alkyl (such as         C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is selected from any of         the groups defined in (c).     -   (17). A compound as defined in any one of paragraphs (1) to         (15), wherein one of R⁹ and R¹⁰ is selected from the group         consisting of H and optionally substituted C₁₋₆ alkyl (such as         C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is selected from the         group consisting of —C(O)R¹⁴, —C(O)OR¹⁴, —C(S)R¹⁴, and         —C(S)OR¹⁴; wherein each R¹⁴ is independently selected from the         group consisting of: (a) optionally substituted C₁₋₆ alkyl, for         example C₁₋₆ alkyl wherein said alkyl is substituted by aryl and         optionally one or two further substituents, and wherein said         aryl is itself optionally substituted, and (b) optionally         substituted aryl.     -   (18). A compound as defined in paragraph (17), where each R¹⁴ is         optionally substituted alkyl having the formula         —(CH₂)_(n)(aryl), wherein n is an integer from 0 to 3, such as 0         or 1, and said aryl is optionally substituted.     -   (19). A compound as defined in any one of paragraphs (16) to         (18), wherein one of R⁹ and R¹⁰ is selected from the group         consisting of H and optionally substituted C₁₋₆ alkyl (such as         C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is —C(O)OR¹⁴.     -   (20). A compound as defined in any one of paragraphs (1) to         (15), wherein one of R⁹ and R¹⁰ is selected from the group         consisting of H and optionally substituted C₁₋₆ alkyl (such as         C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is selected from the         group consisting of —C(O)NR¹⁵R¹⁶ and —C(S)NR¹⁵R¹⁶, wherein each         R¹⁵ and R¹⁶ is independently selected from the group consisting         of (a) H, (b) optionally substituted C₁₋₆ alkyl, for example         C₁₋₆ alkyl wherein said alkyl is substituted by aryl and,         optionally, one or two further substituents, and wherein said         aryl is itself optionally substituted, and (c) optionally         substituted aryl.     -   (21). A compound as defined in paragraph (20), wherein each R¹⁵         and R¹⁶ is independently selected from the group consisting         of (a) H and (b) optionally substituted alkyl having the formula         —(CH₂)_(n)(aryl), wherein n is an integer from 0 to 3, such as 0         or 1, and said aryl is optionally substituted.     -   (22) A compound as defined in claim (20) or (21), wherein one         but not both of R¹⁵ and R¹⁶ is H.     -   (23). A compound as defined in paragraph (2), wherein Z is N or         N-oxide, such as N, W is CR¹, X is CR² and Y is CR³, one of R⁹         and R¹⁰ is selected from the group consisting of H and         optionally substituted C₁₋₆ alkyl (such as C₁₋₃ alkyl), for         example one of R⁹ and R¹⁰ is H, and the other of R⁹ and R¹⁰ is         —C(O)OR¹⁴, wherein each R¹⁴ is independently selected from the         group consisting of: (a) optionally substituted C₁₋₆ alkyl, for         example C₁₋₆ alkyl wherein said alkyl is substituted by aryl         and, optionally, one or two further substituents, and wherein         said aryl is itself optionally substituted, and (b) optionally         substituted aryl.     -   (24). A compound as defined in paragraph (23), wherein R¹⁴ is         optionally substituted alkyl having the formula         —(CH₂)_(n)(aryl), wherein n is an integer from 0 to 3, such as 0         or 1, and said aryl is optionally substituted.     -   (25) A compound as defined in paragraph (23) or (24), wherein         R¹, R² and R³ are each independently selected from the group         consisting of H, halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆         alkyl, such as methyl, substituted aryl, substituted heteroaryl,         —OR wherein R is optionally substituted aryl, and —NHR wherein R         is optionally substituted aryl.     -   (26). A compound as defined in paragraph (23) or (24), wherein         R¹, R² and R³ are each independently selected from the group         consisting of H, halogen, C₁₋₆ alkyl, such as methyl,         substituted aryl, and substituted heteroaryl.     -   (27). A compound as defined in paragraph (23) or (24), wherein         one or two of R¹, R² and R³ is H, and the others of R¹, R² and         R³ that are not H are independently selected from the group         consisting of halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆ alkyl,         such as methyl, substituted aryl, substituted heteroaryl, —OR         wherein R is optionally substituted aryl, and —NHR wherein R is         optionally substituted aryl.     -   (28). A compound as defined in paragraph (23) or (24), wherein         R¹ is H, and one of both of R² and R³ is other than H, wherein         each of R² and R³ that is not H is independently selected from         the group consisting of halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂,         C₁₋₆ alkyl, such as methyl, substituted aryl, substituted         heteroaryl, —OR wherein R is optionally substituted aryl, and         —NHR wherein R is optionally substituted aryl.     -   (29). A compound as defined in any one of paragraphs (23) to         (28), wherein R³ is selected from the group consisting of         halogen, —OR wherein R is optionally substituted aryl, and —NHR         wherein R is optionally substituted aryl.     -   (30). A compound as defined in paragraph (23) or (24), wherein         R¹ is H, and R² and R³ form a saturated or a partially saturated         or a fully unsaturated 5- or 6-membered ring of carbon atoms         optionally including 1 to 3 heteroatoms selected from O, N and S         and the ring is optionally substituted with 1 to 4 substituents         independently selected from R.     -   (31). A compound of Formula I, as defined in any one of         paragraphs (1) to (30) above, or a pharmaceutically acceptable         salt thereof, wherein at least one of R¹, R², R³ and R⁴, where         present, is other than H or methyl, for example wherein at least         one of R¹, R², R³ and R⁴, where present, is other than H or         alkyl, and with the proviso that the compound is not selected         from the following compounds:

-   2-Bromo-N-(5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)acetamide,     N-(6-Phenyl-4-(trifluoromethyl)isoxazolo[5,4-b]pyridin-3-yl)cyclopropanecarboxamide,     and

-   2-Phenyl-N-(6-phenyl-4-(trifluoromethyl)isoxazolo[5,4-b]pyridin-3-yl)acetamide.     -   (32). A compound as defined in paragraph (1), selected from the         group consisting of:

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-(trifluoromethoxy)phenyl)urea     (2)

-   1-(5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-cyanophenyl)urea     (3)

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(2-chlorophenyl)urea     (6)

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(3-chlorophenyl)urea     (7)

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-chlorophenyl)urea     (8)

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(2-(trifluoromethoxy)phenyl)urea     (9)

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(3-(trifluoromethoxy)phenyl)urea     (10)

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(2-methoxyphenyl)urea     (11)

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(3-methoxyphenyl)urea     (12)

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-methoxyphenyl)urea     (13)

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(2-(trifluoromethyl)phenyl)urea     (14)

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-(trifluoromethyl)phenyl)urea     (16)

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-phenylurea     (17)

-   N-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-2-phenylacetamide     (18)

-   N-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-2-(4-(trifluoromethoxy)phenyl)acetamide     (19)

-   Phenyl (5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)carbamate     (4)

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(3-(trifluoromethyl)phenyl)urea     (15)

-   4-Fluorophenyl     (5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)carbamate (5)

-   N-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)acetamide (20)

and pharmaceutically acceptable salts thereof.

-   -   (33). A compound as defined in any one of the preceding         paragraphs (1) to (32), wherein the compound is an IDO1         inhibitor.     -   (34). A compound as defined in any one of the preceding         paragraphs (1) to (32), wherein the compound is a TDO inhibitor.     -   (35). A compound as defined in any one of the preceding         paragraphs (1) to (32), wherein the compound is both an IDO1         inhibitor and a TDO inhibitor.

Certain compounds of the Formula I are novel. Accordingly, such compounds are provided as a further feature of the invention.

In a further aspect, the invention provides a compound of Formula I, as defined in any one of paragraphs (1) to (30) above, or a pharmaceutically acceptable salt thereof, wherein at least one of R¹, R², R³ and R⁴, where present, is other than H or methyl, for example wherein at least one of R¹, R², R³ and R⁴, where present, is other than H or alkyl, and with the proviso that the compound is not selected from the following compounds:

-   2-Bromo-N-(5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)acetamide, -   N-(6-Phenyl-4-(trifluoromethyl)isoxazolo[5,4-b]pyridin-3-yl)cyclopropanecarboxamide,     and -   2-Phenyl-N-(6-phenyl-4-(trifluoromethyl)isoxazolo[5,4-b]pyridin-3-yl)acetamide.

In certain embodiments, the invention provides a compound of Formula I, as defined in any of the paragraphs numbered (35) to (63) below.

-   -   (35). A compound of Formula I or a pharmaceutically acceptable         salt thereof, wherein:

W is CR¹, N or N-oxide;

X is CR², N or N-oxide;

Y is CR³, N or N-oxide;

Z is CR⁴, N or N-oxide;

and where at least one of W, X, Y, and Z is N or N-oxide;

R¹, R², R³ and R⁴ are each independently selected from the following groups: H, halo, R, —OH, —OR, —OC(O)H, —OC(O)R, —OC(O)NH₂, —OC(O)NHR, —OC(O)NRR, —OP(O)(OH)₂, —OP(O)(OR)₂, —NO₂, —NH₂, —NHR, —NRR, —NHC(O)H, —NHC(O)R, —NRC(O)R, —NHC(O)NH₂, —NHC(O)NRR, —NRC(O)NHR, —SH, —SR, —S(O)H, —S(O)R, —SO₂R, —SO₂NH₂, —SO₂NHR, —SO₂NRR, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —CN, —C° CH, —C═CR, —CH═CHR, —CH═CRR, —CR═CHR, —CR═CRR, —CO₂H, —CO₂R, —CHO, —C(O)R, —C(O)NH₂, —C(O)NHR, —C(O)NRR, —CONHSO₂H, —CONHSO₂R, —CONRSO₂R, cyclic C₃-C₇ alkylamino, imidazolyl, C₁-C₆ alkylpiperazinyl, morpholinyl and thiomorpholinyl;

or R¹ and R² taken together, or R² and R³ taken together, or R³ and R⁴ taken together can form a saturated or a partially saturated or a fully unsaturated 5- or 6-membered ring of carbon atoms optionally including 1 to 3 heteroatoms selected from O, N and S, and the ring is optionally substituted independently with 1 to 4 substituents selected from R;

each R is independently selected from any of the groups defined in paragraphs (a) and (b) below:

(a) an optionally substituted C₁₋₆ alkyl group, an optionally substituted C₂₋₆ alkenyl group, an optionally substituted C₂₋₆ alkynyl group and an optionally substituted C₃₋₇ cyclic alkyl group; wherein the one or more optional substituents for each of said alkyl, alkenyl, alkynyl and cyclic alkyl groups are each independently selected from the following groups: halo, —OH, —OR⁵, —OC(O)R⁵, —OC(O)NH₂, —OC(O)NHR⁵, —OC(O)NR⁵R⁵, —OP(O)(OH)₂, —OP(O)(OR⁵)₂, —NO₂, —NH₂, —NHR⁵, —NR⁵R⁵, —N⁺(O⁻)R⁵R⁵, —NHC(O)H, —NHC(O)R⁵, —NR⁵C(O)R⁵, —NHC(O)NH₂, —NHC(O)NR⁵R⁵, —NR⁵C(O)NHR⁵, —SH, —SR⁵, —S(O)H, —S(O)R⁵, —SO₂R⁵, —SO₂NH₂, —SO₂NHR⁵, —SO₂NR⁵R⁵, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —CN, —CO₂H, —CO₂R⁵, —CHO, —C(O)R⁵, —C(O)NH₂, —C(O)NHR⁵, —C(O)NR⁵R⁵, —CONHSO₂H, —C(O)NHSO₂R⁵, —C(O)NR⁵SO₂R⁵, cyclic C₃-C₇ alkylamino, imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl and azetidinyl; wherein each of the groups imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl and azetidinyl are optionally substituted by one or more of the following groups: C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cyclic alkyl, halo, —OH, —OR⁷, —OC(O)R⁷, —OC(O)NH₂—OC(O)NHR⁷, —OC(O)NR⁷R⁷, —OP(O)(OH)₂, —OP(O)(OR⁷)₂, —NO₂, —NH₂, —NHR⁷, —NR⁷R⁷, —N⁺(O⁻) R⁷R⁷, —NHC(O)H, —NHC(O)R⁷, —NR⁷C(O)R⁷, —NHC(O)NH₂, —NHC(O)NR⁷R⁷, —NR⁷C(O)NHR⁷, —SH, —SR⁷, —S(O)H, —S(O)R⁷, —SO₂R⁷, —SO₂NH₂, —SO₂NHR⁷, —SO₂NR⁷R⁷, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R⁷, —CHO, —C(O)R⁷, —C(O)NH₂, —C(O)NHR⁷, —C(O)NR⁷R⁷, —CONHSO₂H, —C(O)NHSO₂R⁷, —C(O)NR⁷SO₂R⁷, an optionally substituted aryl, and an optionally substituted heteroaryl group having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; and wherein the one or more optional substituents for each of said aryl and heteroaryl groups are each independently selected from the following groups: C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl or C₃₋₇ cyclic alkyl, halo, —OH, —OR⁸, —OC(O)R⁸, —OC(O)NH₂, —OC(O)NHR³, —OC(O)NR⁸R⁸, —OP(O)(OH)₂, —OP(O)(OR⁸)₂, —NO₂, —NH₂, —NHR⁸, —NR⁸R⁸, —N⁺(O)R⁸R⁸, —NHC(O)H, —NHC(O)R⁸, —NR⁸C(O)R⁸, —NHC(O)NH₂, —NHC(O)NR⁸R⁸, —NR⁸C(O)NHR⁸, —SH, —SR⁸, —S(O)H, —S(O)R⁸, —SO₂R⁸, —SO₂NH₂, —SO₂NHR⁸, —SO₂NR⁸R⁸, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R⁸, —CHO, —C(O)R⁸, —C(O)NH₂, —C(O)NHR⁸, —C(O)NR⁸R⁸, —CONHSO₂H, —C(O)NHSO₂R⁸, and —C(O)NR⁸SO₂R⁸; wherein each R⁵, R⁷ and R⁸ is independently selected from a C₁₋₆ alkyl group, a C₂₋₆ alkenyl group, a C₂₋₆ alkynyl group and a C₃₋₇ cyclic alkyl group; and

(b) an optionally substituted aryl, and an optionally substituted heteroaryl group having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; and wherein the one or more optional substituents are each independently selected from the same optional substituents as those defined in (a) above for R;

R⁹ and R¹⁰ are each independently selected from any of the groups defined in paragraphs (a) to (d) below, with the proviso that at least one of R⁹ and R¹⁰ is selected from any of the groups defined in paragraphs (c) and (d) below:

(a) H, an optionally substituted C₁₋₆ alkyl group, an optionally substituted C₂₋₆ alkenyl group, an optionally substituted C₂₋₆ alkynyl group, and an optionally substituted C₃₋₇ cyclic alkyl group; wherein the one or more optional substituents for each of said alkyl, alkenyl, alkynyl and cyclic alkyl are each independently selected from the following groups: halo, —OH, —OR¹¹, —OC(O)R¹¹, —OC(O)NH₂, —OC(O)NHR¹¹, —OC(O)NR¹¹R¹¹, —OP(O)(OH)₂, —OP(O)(OR¹¹)₂, —NO₂, —NH₂, —NHR¹¹, —NR¹¹R¹¹, —N⁺(O⁻)R¹¹R¹¹, —NHC(O)H, —NHC(O)R¹¹, —NR¹¹C(O)R¹¹, —NHC(O)NH₂, —NHC(O)NR¹¹R¹¹, —NR¹¹C(O)NHR¹¹, —SH, —SR¹¹, —S(O)H, —S(O)R¹¹, —SO₂R¹¹, —SO₂NH₂, —SO₂NHR¹¹, —SO₂NR¹¹R¹¹, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R¹¹, —CHO, —C(O)R¹¹, —C(O)NH₂, —C(O)NHR¹¹, —C(O)NR¹¹R¹¹, —CONHSO₂H, —C(O)NHSO₂R¹¹, —C(O)NR¹¹SO₂R¹¹, cyclic C₃-C₇ alkylamino, imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl, azetidinyl, aryl, and heteroaryl having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; wherein each of the groups cyclic C₃-C₇ alkylamino, imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl azetidinyl, aryl and heteroaryl are optionally substituted by one or more of the following groups: C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cyclic alkyl, halo, —OH, —OR¹³, —OC(O)R¹³, —OC(O)NH₂, —OC(O)NHR¹³, —OC(O)NR¹³R¹³, —OP(O)(OH)₂, —OP(O)(OR¹³)₂, —NO₂, —NH₂, —NHR¹³, —NR¹³R¹³, —N⁺(O⁻)R¹³R¹³, —NHC(O)H, —NHC(O)R¹³, —NR¹³C(O)R¹³, —NHC(O)NH₂, —NHC(O)NR¹³R¹³, —NR¹³C(O)NHR¹³, —SH, —SR¹³, —S(O)H, —S(O)R¹³, —SO₂R¹³, —SO₂NH₂, —SO₂NHR¹³, —SO₂NR¹³R¹³, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R¹³, —CHO, —C(O)R¹³, —C(O)NH₂, —C(O)NHR¹³, —C(O)NR¹³R¹³, —CONHSO₂H, —C(O)NHSO₂R¹³, and —C(O)NR¹³SO₂R¹³; wherein each R¹¹ and R¹³ is independently selected from a C₁₋₆ alkyl group, a C₂₋₆ alkenyl group, a C₂₋₆ alkynyl group and a C₃₋₇ cyclic alkyl group;

(b) an optionally substituted aryl, and an optionally substituted heteroaryl group having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; and wherein the one or more optional substituents for each of said aryl and heteroaryl are each independently selected from the same optional substituents as those defined in (a) above for R⁹ and R¹⁰;

(c) —C(O)R¹⁴, —C(O)OR¹⁴, —C(O)NR¹⁵R¹⁶, —C(O)SR¹⁴, —C(S)R¹⁴, —C(S)OR¹⁴ C(S)NR¹⁵R¹⁶, and —C(S)SR¹⁴, wherein each R¹⁴, R¹⁵ and R¹⁶ is independently selected from the group consisting of H, optionally substituted C₁₋₆ alkyl, optionally substituted C₂₋₆ alkenyl, optionally substituted C₂₋₆ alkynyl, optionally substituted C₃₋₇ cyclic alkyl, optionally substituted aryl, and optionally substituted heteroaryl having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S, and wherein the one or more optional substituents for each of said alkyl, alkenyl, alkynyl, cyclic alkyl, aryl and heteroaryl for R¹⁴, R¹⁵ and R¹⁶ are each independently selected from the same optional substituents as those defined in (a) above for R⁹ and R¹⁰; and

(d) —SO₂(CRR)_(n)R¹⁷, wherein n is an integer of from 0 to 6, each R is independently selected from the groups defined above for R, and R¹⁷ is optionally substituted aryl or optionally substituted heteroaryl having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S, and wherein the one or more optional substituents for each of said aryl and heteroaryl are independently selected from the same optional substituents as those defined in (a) above for R⁹ and R¹⁰; and —SO₂R¹⁸, wherein R¹⁸ is optionally substituted C₁₋₆alkyl or optionally substituted C₃₋₇ cyclic alkyl, wherein the one or more optional substituents for each of said alkyl and cyclic alkyl are each independently selected from those defined in (a) above for R⁹ and R¹⁰;

with the proviso that at least one of R¹, R², R³ and R⁴, where present, is other than H or methyl, and

with the further proviso that the compound is not selected from the following: 2-Bromo-N-(5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)acetamide,

-   N-(6-Phenyl-4-(trifluoromethyl)isoxazolo[5,4-b]pyridin-3-yl)cyclopropanecarboxamide,     and -   2-Phenyl-N-(6-phenyl-4-(trifluoromethyl)isoxazolo[5,4-b]pyridin-3-yl)acetamide.     -   (36). A compound according to paragraph (35), wherein Z is N or         N-oxide, such as N, W is CR¹, X is CR² and Y is CR³.     -   (37). A compound according to paragraph (35), wherein X is N or         N-oxide, such as N, W is CR¹, Y is CR³ and Z is CR⁴.     -   (38). A compound according to paragraph (35), wherein X and Z         are both N or N-oxide, such as N, W is CR¹ and Y is CR³.     -   (39). A compound according to any one of paragraphs (35) to         (38), wherein R¹, R², R³ and R⁴, where present, are each         independently selected from the group consisting of H, halo,         optionally substituted C₁-C₆ alkyl, —O—R wherein R is selected         from optionally substituted C₁-C₆ alkyl and optionally         substituted aryl (such as phenyl), —NHR wherein R is optionally         substituted aryl, an optionally substituted aryl, and an         optionally substituted heteroaryl group having up to 12 carbon         atoms and having one or more heteroatoms in its ring system         which are each independently selected from O, N and S.     -   (40). A compound according to paragraph (39), wherein R¹, R², R³         and R⁴, where present, are each independently selected from the         group consisting of H, halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆         alkyl, such as methyl, substituted aryl, substituted heteroaryl,         —OR wherein R is optionally substituted aryl, and —NHR wherein R         is optionally substituted aryl.     -   (41). A compound according to paragraph (39), wherein one or two         of R¹, R², R³ and R⁴, where present, is H, and the others of R¹,         R², R³ and R⁴ that are not H are independently selected from the         group consisting of halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆         alkyl, such as methyl, substituted aryl, substituted heteroaryl,         —OR wherein R is optionally substituted aryl, and —NHR wherein R         is optionally substituted aryl.     -   (42). A compound according to any one of paragraphs (39) to         (41), wherein R³ is present and selected from the group         consisting of halogen, —OR wherein R is optionally substituted         aryl, and —NHR wherein R is optionally substituted aryl.     -   (43). A compound according to paragraph (36), wherein Z is N or         N-oxide, such as N, W is CR¹, X is CR² and Y is CR³, and R³ is         selected from the group consisting of halogen, —O—R wherein R is         optionally substituted aryl, and —NHR wherein R is optionally         substituted aryl.     -   (44). A compound according to paragraph (36), wherein Z is N or         N-oxide, such as N, W is CR¹, X is CR² and Y is CR³, R¹ is H,         and one or both of R² and R³ are other than H, for example, both         R² and R³ are other than H, or R² is H and R³ is other than H,         or R³ is H and R² is other than H.     -   (45). A compound according to paragraph (44), wherein each of R²         and R³ that is other than H is independently selected from the         group consisting of halogen, optionally substituted C₁-C₆ alkyl,         —OR wherein R is selected from optionally substituted C₁-C₆         alkyl and optionally substituted aryl, —NHR wherein R is         optionally substituted aryl; an optionally substituted aryl,         such as substituted phenyl, and an optionally substituted         heteroaryl group.     -   (46). A compound according to paragraph (45), wherein each of R²         and R³ that is other than H is independently selected from the         group consisting of halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆         alkyl such as methyl, substituted aryl, substituted heteroaryl,         —OR wherein R is optionally substituted aryl, and —NHR wherein R         is optionally substituted aryl.     -   (47). A compound according to any one of paragraphs (35) to         (38), wherein R¹ and R² taken together, or R² and R³ taken         together, or R³ and R⁴ taken together, form a saturated or a         partially saturated or a fully unsaturated 5- or 6-membered ring         of carbon atoms optionally including 1 to 3 heteroatoms selected         from O, N or S and the ring is optionally substituted with 1 to         4 substituents independently selected from R, and those of R¹,         R², R³ and R⁴ that are not part of the ring, are independently         selected from: H, halo, optionally substituted C₁-C₆ alkyl, O—R         wherein R is optionally substituted C₁-C₆ alkyl, an optionally         substituted aryl and an optionally substituted heteroaryl group         having up to 12 carbon atoms and having one or more heteroatoms         in its ring system which are each independently selected from O,         N and S.     -   (48). A compound according to any one of paragraphs (35) to         (47), wherein one of R⁹ and R¹⁰ is selected from the group         consisting of H and optionally substituted C₁₋₆ alkyl (such as         C₁₋₃ alkyl), for example one of one of R⁹ and R¹⁰ is H, and the         other of R⁹ and R¹⁰ is selected from any of the groups defined         in paragraphs (c) and (d).     -   (49). A compound according to any one of paragraphs (35) to         (48), wherein one of R⁹ and R¹⁰ is selected from the group         consisting of H and optionally substituted C₁₋₆ alkyl (such as         C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is selected from any of         the groups defined in paragraph (c).     -   (50). A compound according to any one of paragraphs (35) to         (48), wherein one of R⁹ and R¹⁰ is selected from the group         consisting of H and optionally substituted C₁₋₆ alkyl (such as         C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is selected from the         group consisting of —C(O)R¹⁴, —C(O)OR¹⁴, —C(S)R¹⁴, and         —C(S)OR¹⁴; wherein each R¹⁴ is independently selected from the         group consisting of: (a) optionally substituted C₁₋₆ alkyl, for         example C₁₋₆ alkyl wherein said alkyl is substituted by aryl and         optionally one or two further substituents, and wherein said         aryl is itself optionally substituted, and (b) optionally         substituted aryl.     -   (51). A compound according to paragraph (50), where each R¹⁴ is         optionally substituted alkyl having the formula         —(CH₂)_(n)(aryl), wherein n is an integer from 0 to 3, such as 0         or 1, and said aryl is optionally substituted.     -   (52). A compound according to any one of paragraphs (49) to         (51), wherein one of R⁹ and R¹⁰ is selected from the group         consisting of H and optionally substituted C₁₋₆ alkyl (such as         C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is —C(O)OR¹⁴.     -   (53). A compound according to any one of paragraphs (35) to         (48), wherein one of R⁹ and R¹⁰ is selected from the group         consisting of H and optionally substituted C₁₋₆ alkyl (such as         C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is selected from the         group consisting of —C(O)NR¹⁵R¹⁶ and —C(S)NR¹⁵R¹⁶, wherein each         R¹⁵ and R¹⁶ is independently selected from the group consisting         of (a) H, (b) optionally substituted C₁₋₆ alkyl, for example         C₁₋₆ alkyl wherein said alkyl is substituted by aryl and,         optionally, one or two further substituents, and wherein said         aryl is itself optionally substituted, and (c) optionally         substituted aryl.     -   (54). A compound according to paragraph (53), wherein each R¹⁵         and R¹⁶ is independently selected from the group consisting         of (a) H and (b) optionally substituted alkyl having the formula         —(CH₂)_(n)(aryl), wherein n is an integer from 0 to 3, such as 0         or 1, and said aryl is optionally substituted.     -   (55). A compound according to paragraph (53) or (54), wherein         one but not both of R¹⁵ and R¹⁶ is H.     -   (56). A compound according to paragraph (36), wherein Z is N or         N-oxide, such as N, W is CR¹, X is CR² and Y is CR³, one of R⁹         and R¹⁰ is selected from the group consisting of H and         optionally substituted C₁₋₆ alkyl (such as C₁₋₃ alkyl), for         example one of R⁹ and R¹⁰ is H, and the other of R⁹ and R¹⁰ is         —C(O)OR¹⁴, wherein each R¹⁴ is independently selected from the         group consisting of: (a) optionally substituted C₁₋₆ alkyl, for         example C₁₋₆ alkyl wherein said alkyl is substituted by aryl         and, optionally, one or two further substituents, and wherein         said aryl is itself optionally substituted, and (b) optionally         substituted aryl.     -   (57). A compound according to paragraph (56), wherein R¹⁴ is         optionally substituted alkyl having the formula         —(CH₂)_(n)(aryl), wherein n is an integer from 0 to 3, such as 0         or 1, and said aryl is optionally substituted.     -   (58). A compound according to paragraph (56) or (57), wherein         R¹, R² and R³ are each independently selected from the group         consisting of H, halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆         alkyl, such as methyl, substituted aryl, substituted heteroaryl,         —OR wherein R is optionally substituted aryl, and —NHR wherein R         is optionally substituted aryl.     -   (59). A compound according to paragraph (56) or (57), wherein         R¹, R² and R³ are each independently selected from the group         consisting of H, halogen, C₁₋₆ alkyl, such as methyl,         substituted aryl, and substituted heteroaryl.     -   (60). A compound according to paragraph (56) or (57), wherein         one or two of R¹, R² and R³ is H, and the others of R¹, R² and         R³ that are not H are independently selected from the group         consisting of halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆ alkyl,         such as methyl, substituted aryl, substituted heteroaryl, —OR         wherein R is optionally substituted aryl, and —NHR wherein R is         optionally substituted aryl.     -   (61). A compound according to paragraph (56) or (57), wherein R¹         is H, and one of both of R² and R³ is other than H, wherein each         of R² and R³ that is not H is independently selected from the         group consisting of halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆         alkyl, such as methyl, substituted aryl, substituted heteroaryl,         —OR wherein R is optionally substituted aryl, and —NHR wherein R         is optionally substituted aryl.     -   (62). A compound according to any one of paragraphs (56) to         (61), wherein R³ is selected from the group consisting of         halogen, —OR wherein R is optionally substituted aryl, and —NHR         wherein R is optionally substituted aryl.     -   (63). A compound according to paragraph (56) or (57), wherein R¹         is H, and R² and R³ form a saturated or a partially saturated or         a fully unsaturated 5- or 6-membered ring of carbon atoms         optionally including 1 to 3 heteroatoms selected from O, N and S         and the ring is optionally substituted with 1 to 4 substituents         independently selected from R.

By way of example, the invention further provides a compound of Formula I selected from the following:

-   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-(trifluoromethoxy)phenyl)urea     (2) -   1-(5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-cyanophenyl)urea     (3) -   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(2-chlorophenyl)urea     (6) -   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(3-chlorophenyl)urea     (7) -   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-chlorophenyl)urea     (8) -   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(2-(trifluoromethoxy)phenyl)urea     (9) -   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(3-(trifluoromethoxy)phenyl)urea     (10) -   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(2-methoxyphenyl)urea     (11) -   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(3-methoxyphenyl)urea     (12) -   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-methoxyphenyl)urea     (13) -   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(2-(trifluoromethyl)phenyl)urea     (14) -   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-(trifluoromethyl)phenyl)urea     (16) -   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-phenylurea     (17) -   N-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-2-phenylacetamide     (18) -   N-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-2-(4-(trifluoromethoxy)phenyl)acetamide     (19) -   Phenyl (5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)carbamate     (4) -   1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(3-(trifluoromethyl)phenyl)urea     (15) -   4-Fluorophenyl     (5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)carbamate (5) -   N-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)acetamide (20);

and pharmaceutically acceptable salts thereof.

Other aspects of the invention may include suitable combinations of embodiments disclosed herein. Also, as will be appreciated by one of skill in the art, features and preferred embodiments of one aspect of the invention will also pertain to other aspects of the invention.

While the invention is broadly as defined above, it is not limited thereto and also includes embodiments of which the following description provides examples. The invention will now be described in more detail.

DETAILED DESCRIPTION OF THE INVENTION Definitions

As used herein, the term “radiotherapy” means the use of high-energy radiation from x-rays, gamma rays, neutrons, protons, and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy). Systemic radiotherapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that travels in the blood to tissues throughout the body. The terms irradiation and radiation therapy have the same meaning.

It is to be recognised that certain compounds of the present invention may exist in one or more different enantiomeric or diastereomeric forms. It is to be understood that the enantiomeric or diastereomeric forms are included in the above aspects of the invention.

The term halo or halogen group used throughout the specification is to be taken as meaning a fluoro, chloro, bromo or iodo group.

It is to be understood that where variables of the Formula I as defined above are optionally substituted by one or more imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl and azetidinyl groups that the linkage to the relevant variable may be through either one of the available nitrogen or carbon ring atoms of these groups.

It is to be understood that the term “heteroaryl” includes both monocyclic and bicyclic ring systems, unless the context requires otherwise.

It is to be understood that the term “aryl” means an aromatic hydrocarbon such as phenyl or naphthyl.

It is to be understood that where a group is qualified as being “optionally substituted”, this means that the group can be either (a) unsubstituted or (b) substituted by one or more of the defined substituents.

It is to be understood that where reference is made throughout the specification to a C₁-C₆ alkyl or C₂-C₆ alkenyl group, these groups may be unbranched or branched. For example, it is intended that reference to a C₁-C₆ alkyl would include a tert-butyl (Me)₃C— group.

The expressions “treating cancer” and ‘treatment of cancer” include methods that produce one or more anti-cancer effects which include, but are not limited to, anti-tumor effects, the response rate, the time to disease progression and the overall survival rate. “Anti-tumor” effects include but are not limited to inhibition of tumor growth, tumor growth delay, regression of tumor, shrinkage of tumor, increased time to regrowth of tumor on cessation of treatment and slowing of disease progression.

“Therapeutically effective amount” means an amount of a compound that, when administered to a subject for treating a cancer, is sufficient to effect such treatment for the cancer. The “effective amount” will vary depending on the cancer to be treated, the compound to be administered, the severity of the cancer treated, the age and relative health of the subject, the route and form of administration, whether the treatment is monotherapy or combination therapy, the judgement of the attending clinician, and other factors.

“Pharmaceutically acceptable” means: that which is useful in preparing a pharmaceutical composition that is generally safe, non-toxic, and neither biologically nor otherwise undesirable, and includes that which is acceptable for veterinary as well as human pharmaceutical use.

“Pharmaceutically acceptable salts” of a compound means salts that are pharmaceutically acceptable, as defined herein, and that possess the desired pharmacological activity of the parent compound. Such salts include:

-   -   (a) acid addition salts formed with inorganic acids such as         hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid,         phosphoric acid and the like; or formed with organic acids such         as acetic acid, methanesulfonic acid, maleic acid, tartaric         acid, citric acid and the like; and     -   (b) salts formed when an acidic proton present in the parent         compound either is replaced by a metal ion, e.g. an alkali metal         ion, an alkaline earth ion, or an aluminium ion; or coordinates         with an organic or inorganic base. Acceptable organic bases         include ethanolamine, diethanolamine, N-methylglucamine,         triethanolamine and the like. Acceptable inorganic bases include         aluminium hydroxide, calcium hydroxide, potassium hydroxide,         sodium carbonate and sodium hydroxide.

“Warm blooded animal” means any member of the mammalia class including, but not limited to humans, non-human primates such as chimpanzees and other apes and monkey species, farm animals such as cattle, horses, sheep, goats, and swine; domestic animals such as rabbits, dogs and cats; laboratory animals including rodents, such as rats, mice and guinea pigs, and the like.

Compounds of the Invention and Methods of Preparing them

As defined above, in broad terms the invention relates to pharmaceutical compositions containing compounds of the general Formula I, and the use of such compounds in therapy, and in particular cancer therapy. Compounds of Formula I have been found to be inhibitors of indoleamine 2,3-dioxygenase 1 (IDO1) and/or tryptophan2,3-dioxygenase (TDO). As such, the compounds of the present invention are expected to be useful in cancer therapy, either alone or in combination with other agents, such as anti-cancer vaccines, modulators of immune checkpoint proteins, adoptive T cell immunotherapies (for example chimeric antigen receptor T cells (CART cells)), radiation therapy and other chemotherapeutic agents. The compounds of Formula I are also expected to be useful in the treatment of various other conditions besides cancer, as described in more detail in the Therapeutic Methods of the Invention section, below.

Certain methods for preparing compounds and pharmaceutically acceptable salts of the compounds of Formula I are described below, with reference to Methods 1 to 11.

Synthetic Schemes

Methods 1 to 8 below describe the preparation of precursor 3-amino compounds, which can be used as starting materials to prepare compounds of the formula I of the present invention, using the processes described in Methods 9 to 11 below, or using analogous processes.

Certain precursor 3-amino compounds may be prepared by reaction of an appropriately substituted halo-cyano pyridine with acetohydroxamic acid, in the presence of a base such as potassium tert-butoxide, potassium carbonate or cesium carbonate (Method 1). A range of solvents may be used for this reaction, including DMF, p-dioxane and N-methylmorpholine.

Method 1

Compounds bearing alkylamino substituents and/or arylamino substituents may be prepared by displacement of an activated halogen atom with amines and/or anilines (Method 2).

Method 2

Compounds containing alkyl substitution on the exocyclic amino group may be prepared by reaction of the primary amine with a trialkylorthoformate, followed by reduction with an appropriate reducing agent, such as sodium borohydride (Method 3).

Method 3

Such compounds may also be prepared by reaction of the primary amine with an alkyl aldehyde, followed by a reducing agent such as sodium cyanoborohydride, in a reductive amination process (Method 4).

Method 4

Compounds bearing a pendant aryl or heteroaryl (Het) substituent may be prepared by reaction of an appropriately substituted halogen- or triflate-containing substrate with suitable aryl or heteroaryl boronic acids or esters, under palladium catalysis, in a Suzuki coupling reaction (Method 5).

Method 5

Compounds bearing a pendant aryl or heteroaryl (Het) substituent may also be prepared by performing a palladium-catalysed Suzuki coupling reaction with an appropriately substituted halogen or O-triflate containing chemical intermediate, and suitable aryl or heteroaryl boronic acids or esters, followed by elaboration of the resultant aryl- or heteroarylated product to the final product (Method 6).

Method 6

Compounds containing alkyl and/or aryl ether-linked substituents may be prepared by displacement of an activated halogen atom by alcohols and/or phenols, in the presence of a base such as sodium or sodium hydride or cesium carbonate (Method 7).

Method 7

Compounds containing thioalkyl and/or thioaryl ether-linked substituents may be prepared by displacement of an activated halogen atom by thiols and/or thiophenols, in the presence of a base such as sodium or sodium hydride or cesium carbonate, or by direct reaction with the metal salt of a thiol or thiophenol. The resultant thioalkyl or thiophenol derivatives may be oxidised to their corresponding sulfoxide or sulfone derivatives with suitable oxidising reagents such as hydrogen peroxide, peracids, metal complexes and oxaziridines (Method 8).

Method 8

Compounds of Formula I according to the present invention, containing urea functionality at the 3-position of the isoxazolopyridine ring system, can be prepared by reaction of the corresponding 3-amino compound with an alkyl, aryl or heteroaryl isocyanate. In some instances the reaction can be mediated by the addition of a suitable catalyst, such as dibutyltin oxide (Method 9). The corresponding thioureas may be similarly prepared by reacting the 3-aminoisoxazolopyridine with analogous isothiocyanates.

Method 9

Compounds of Formula I according to the present invention, containing carbamate functionality at the 3-position of the isoxazolopyridine ring system, can be prepared by reaction of the corresponding 3-amino compound with an alkyl, aryl or heteroaryl chloroformate in the presence of a base, such as Et₃N, pyridine, K₂CO₃ and the like (Method 10). The corresponding thiocarbamates may be similarly prepared by reacting the 3-aminoisoxazolopyridine with analogous chlorothioformates. The carbamates and thiocarbamates so-produced may further be used to prepare compounds containing urea and thiourea functionality, respectively at the 3-position of the isoxazolopyridine ring system, by their reaction with alkyl amines, substituted anilines, or amino-substituted heterocycles (Method 10). The carbamates and thiocarbamates so-produced may also be reacted with alkyl thiols, substituted thiophenols and heterocyclic thiols to produce corresponding S-linked thiocarbamates and dithiocarbamates, respectively.

Method 10

Compounds of Formula I according to the present invention, containing amide functionality at the 3-position of the isoxazolopyridine ring system, may be prepared by reaction of an alkyl, or aryl, or heterocyclic carboxylic acid with an activating reagent such as thionyl chloride, N,N-carbonyldiimidazole, EDCI and the like, followed by reaction of the resulting species with the 3-aminoisoxazolopyridine. A base such as NaH, Et₃N, pyridine, K₂CO₃ and the like may be used in both reaction steps, and a catalyst such as 4-N,N-(dimethylamino)pyridine may be used in the final coupling reaction (Method 11). The amides so-produced may be converted into corresponding thioamides by thiiation with a suitable reagent, such as P₄S₁₀ or Lawesson's reagent, in a suitable solvent such as pyridine, tertrahydrofuran, benzene and the like.

Method 11

Compounds of Formula I according to the present invention, containing sulfonamide functionality at the 3-position of the isoxazolopyridine ring system, can be prepared by reaction of the corresponding 3-amino compound with an alkyl, aryl or heteroaryl sulfonyl chloride in the presence of a base, such as Et₃N, pyridine, K₂CO₃ and the like (Method 12).

Method 12

The procedures of Methods 9 to 12 can also be carried out on isoxazolopyridines where a mono-alkylamino group, or a mono-arylamino group, or a mono-heteroarylamino group has been introduced at the 3-position by the procedures, for example, of Methods 3 and 4, to give N-alkylated, N-arylated and N-heteroarylated derivatives of the 3-position amides, thioamides, carbamates, thiocarbamates, ureas, thioureas, dithiocarbamates and sulfonamides.

Those persons skilled in the art will understand that by using analogous procedures to those outlined above, other compounds of the Formula I can also be prepared.

Therapeutic Methods of the Invention

The compounds of Formula I of the invention may be inhibitors of IDO1 or TDO, or both IDO1 and TDO. Compounds that are inhibitors of either IDO1 or TDO, and compounds that are dual inhibitors of IDO1 and TDO, are expected to be useful in cancer therapy. Accordingly, in certain embodiments, the present invention provides methods of treating cancer in warm blooded animals, including humans, by administering to a subject in need of such treatment a therapeutically effective amount of a compound of Formula I, or a pharmaceutical composition containing a compound of Formula I.

In particular aspects of the invention, the compounds of formula I are expected to be useful in restoring tumor immunity in cancer patients. The compounds of the invention may be useful either alone, or in combination with other cancer therapies, including chemotherapeutic agents, radiation and/or immune modulating agents.

Immune modulating agents include, without limitation, anti-cancer vaccines, agents that modulate immune checkpoint proteins (such as CTLA4 and the PD1-4s, LAG3 and TIM3) and adoptive T-cell therapies (such as CARTs). Accordingly, the compound of Formula I can be administered either alone or in combination with one or more other such therapies, either simultaneously or sequentially dependent upon the particular condition to be treated.

In particular embodiments, the compound of Formula I may be administered in combination with one or more immunotherapies selected from Ipilimumab, Tremelimumab (both inhibitors of CTLA4), Nivolumab, Pembrolizumab (also known as Lambrolizumab), and Pidilizumab (all inhibitors of PD-1).

Additional chemotherapeutic agents that can be administered in combination with a compound of Formula I include but are not limited to compounds listed on the cancer chemotherapy drug regimens in the 14^(th) Edition of the Merck Index (2006), which is hereby incorporated by reference, such as asparaginase, bleomycin, carboplatin, carmustine, chlorambucil, cisplatin, colaspase, cyclophosphamide, cytarabine, dacarbazine, dactinomycin, daunorubicin, doxorubicin (adriamycin), epirubicin, etoposide, 5-fluorouracil, hexamethylmelamine, hydroxyurea, ifosfamide, irinotecan, leucovorin, lomustine, mechlorethamine, 6-mercaptopurine, mesna, methotrexate, mitomycin C, mitoxantrone, prednisolone, prednisone, procarbazine, raloxifen, streptozocin, tamoxifen, thioguanine, topotecan, vinblastine, vincristine, and vindesine.

Additional anti-proliferative agents that can be administered in combination with a compound of Formula I include but are not limited to BCNU, CCNU, DTIC, and actinomycin D. Still further anti-proliferative agents include but are not limited to those compounds acknowledged to be used in the treatment of neoplastic diseases in Goodman and Gilman's The Pharmacological Basis of Therapeutics (Eleventh Edition), editor Molinoff et al., publ. by McGraw-Hill, pages 1225-1287 (2006), which is hereby incorporated by reference, such as aminoglutethimide, L-asparaginase, azathioprine, 5-azacytidine cladribine, busulfan, diethylstilbestrol, 2′,2′-difluorodeoxycytidine, docetaxel, erythrohydroxynonyladenine, ethinyl estradiol, 5-fluorodeoxyuridine, 5-fluorodeoxyuridine monophosphate, fludarabine phosphate, fluoxymesterone, flutamide, hydroxyprogesterone caproate, idarubicin, interferon, medroxyprogesterone acetate, megestrol acetate, melphalan, mitotane, paclitaxel, pentostatin, N-phosphonoacetyl-L-aspartate (PALA), plicamycin, semustine, teniposide, testosterone propionate, thiotepa, trimethylmelamine, uridine, and vinorelbine.

Additional anti-proliferative agents that can be administered in combination with a compound of Formula I include but are not limited to other molecular targeted agents, which block the growth of cancer cells by interfering with specific targeted molecules needed for carcinogenesis and tumour growth. Examples include small molecule protein and lipid kinase inhibitors, monoclonal antibodies, molecularly targeted humanised monoclonal antibodies and monoclonal antibody drug conjugates. Examples of such inhibitors include: Rituximab, Trastuzumab, Alemtuzumab, Tositumomab-I131, Cetuximab, Ibritumomab tiuxetan, Bevacizumab, Panitumumab, Ofatumumab, Ipilimumab, Brentuximab vedotin, Pertuzumab, Ado-Trastuzumab emtansine, Ramucirumab, Obinutuzumab, Nivolumab, Lambrolizumab, Dinutuximab, Imatinib, Gefitinib, Erlotinib, Sorafenib, Dasatinib, Sunitinib, Lapatinib, Nilotinib, Pazopanib, Crizotinib, Ruxolitinib, Vandetanib, Vemurafenib, Axitinib, Bosutinib, Cabozantinib, Ponatinib, Regorafenib, Tofacitinib, Afatinib, Dabrafenib, Ibrutinib and Trametinib.

A wide range of cancers may be treated by the compounds of the present invention. Cancers that may be treated in accordance with the present invention include but are not limited to: colorectal cancer, cancers of the breast, melanoma, reproductive organs, respiratory tract, brain, digestive tract, urinary tract, eye, liver, skin, head and neck, thyroid, parathyroid and their distant metastases. Those disorders also include lymphomas, sarcomas, and leukemias.

Examples of breast cancer include, but are not limited to invasive ductal carcinoma, invasive lobular carcinoma, ductal carcinoma in situ, and lobular carcinoma in situ.

Examples of cancers of the respiratory tract include, but are not limited to small-cell and non-small-cell lung carcinoma, as well as bronchial adenoma and pleuropulmonary blastoma.

Examples of brain cancers include, but are not limited to brain stem and hypophthalmic glioma, cerebellar and cerebral astrocytoma, medulloblastoma, ependymoma, as well as neuroectodermal and pineal tumor.

Tumors of the male reproductive organs include, but are not limited to prostate and testicular cancer.

Tumors of the female reproductive organs include, but are not limited to endometrial, cervical, ovarian, vaginal, and vulvar cancer, as well as sarcoma of the uterus.

Tumors of the digestive tract include, but are not limited to anal, colon, colorectal, esophageal, gallblader, gastric, pancreatic, rectal, small-intestine, and salivary gland cancers.

Tumors of the urinary tract include, but are not limited to bladder, penile, kidney, renal pelvis, ureter, and urethral cancers.

Eye cancers include, but are not limited to intraocular melanoma and retinoblastoma.

Examples of liver cancers include, but are not limited to hepatocellular carcinoma (liver cell carcinomas with or without fibrolamellar variant), cholangiocarcinoma (intrahepatic bile duct carcinoma), and mixed hepatocellular cholangiocarcinoma.

Skin cancers include, but are not limited to squamous cell carcinoma, Kaposi's sarcoma, malignant melanoma, Merkel cell skin cancer, and non-melanoma skin cancer.

Head-and-neck cancers include, but are not limited to laryngeal/hypopharyngeal/nasopharyngeal/oropharyngeal cancer, and lip and oral cavity cancer. Lymphomas include, but are not limited to AIDS-related lymphoma, non-Hodgkin's lymphoma, cutaneous T-cell lymphoma, Hodgkin's disease, and lymphoma of the central nervous system.

Sarcomas include, but are not limited to sarcoma of the soft tissue, osteosarcoma, malignant fibrous histiocytoma, lymphosarcoma, and rhabdomyosarcoma. Leukemias include, but are not limited to acute myeloid leukemia, acute lymphoblastic leukemia, chronic lymphocytic leukemia, chronic myelogenous leukemia, and hairy cell leukemia.

These disorders have been well characterized in man, but also exist with a similar etiology in other warm-blooded animals, and can be treated by the compounds of the present invention.

It will be appreciated by those skilled in the art that a particular method of therapy will employ a selected route of administration which will in turn depend on a variety of factors, all of which are considered routinely when administering therapeutics. It will be further appreciated by one skilled in the art that the optimal course of treatment, i.e., the mode of treatment and the daily number of doses of a compound of this invention given for a defined number of days, can be ascertained by those skilled in the art using conventional treatment tests.

Therapeutic dosages will likely be in the range of 1 mg to 30 g per day. The specific dose level selected for any particular patient will depend upon a variety of factors, including the activity of the specific compound employed, the age, body weight, general health, sex, diet, time of administration, route of administration, and rate of excretion, drug combination and the severity of the condition undergoing therapy.

Certain compounds of Formula I, as well as being inhibitors of IDO1, may also inhibit IDO2. Compounds that are dual inhibitors of IDO1 and IDO2 are also expected to be useful in cancer therapy. Accordingly, in another aspect, the invention provides a method of inhibiting IDO1 and IDO2 in a warm blooded animal in need thereof, including a human, comprising administering to the animal a compound of Formula I or a pharmaceutically acceptable salt thereof, in an amount effective to inhibit IDO1 and IDO2.

It has been reported that compounds that are inhibitors of IDO (IDO1 and IDO2) and/or TDO may have efficacy not only in the treatment of cancer, but also in the treatment of a range of other diseases or conditions, for example as discussed in PCT International Publication WO 2015/082499 and the references to scientific literature referred to therein, all of which are incorporated herein by reference. For example, such compounds may be useful in the treatment of inflammatory conditions, infectious diseases, central nervous system diseases or disorders, coronary heart disease, chronic renal failure, post anaesthesia cognitive dysfunction, disease conditions or disorders relating to female reproductive health, and cataracts. Accordingly, compounds of Formula I of the present invention may also be useful in the treatment of such diseases or conditions.

Examples of inflammatory conditions that may be treated by compounds of Formula I include conditions relating to immune B cell, T cell, dendritic cell, natural killer cell, macrophage, and/or neutrophil dysregulation.

Examples of infectious diseases that may be treated by compounds of Formula I include bacterial infections, viral infections such as gut infections, hepatitis C, sepsis, and sepsis induced hypotension.

Examples of central nervous system diseases or disorders that may be treated by compounds of Formula I include amyotrophic lateral sclerosis (AML), Huntington's disease, Alzheimer's disease, pain, psychiatric disorders including affective disorders such as depression, multiple sclerosis, Parkinson's disease, and HIV related neurocognitive decline.

An example of diseases or disorders relating to female reproductive health that may be treated by compounds of Formula I is endometriosis, and conditions relating to female reproductive health include contraception and abortion.

Pharmaceutical Compositions of the Invention

The invention includes pharmaceutical compositions including one or more compounds of Formula I of this invention, and a pharmaceutically acceptable carrier.

The pharmaceutically acceptable excipient, adjuvant, carrier, buffer or stabiliser should be nontoxic and should not interfere with the efficacy of the active ingredient. The precise nature of the carrier or other material will depend on the route of administration.

The compounds may be administered orally, topically, parenterally, by inhalation or spray or rectally in dosage unit formulations. The term ‘administration by injection’ includes intravenous, intramuscular, subcutaneous and parenteral injections, as well as use of infusion techniques. One or more compounds may be present in association with one or more non-toxic pharmaceutically acceptable carriers and if desired other active ingredients.

Compositions intended for oral use may be prepared according to any suitable method known to the art for the manufacture of pharmaceutical compositions. Such compositions may contain one or more agents selected from the group consisting of diluents, sweetening agents, flavoring agents, coloring agents and preserving agents in order to provide palatable preparations. Tablets contain the active ingredient in admixture with non-toxic pharmaceutically acceptable excipients which are suitable for the manufacture of tablets. These excipients may be, for example, inert diluents, such as calcium carbonate, sodium carbonate, lactose, calcium phosphate or sodium phosphate; granulating and disintegrating agents, for example, corn starch, or alginic acid; and binding agents, for example magnesium stearate, stearic acid or talc. The tablets may be uncoated or they may be coated by known techniques to delay disintegration and adsorption in the gastrointestinal tract and thereby provide a sustained action over a longer period. For example, a time delay material such as glyceryl monostearate or glyceryl distearate may be employed. These compounds may also be prepared in solid, rapidly released form.

Formulations for oral use may also be presented as hard gelatin capsules wherein the active ingredient is mixed with an inert solid diluent, for example, calcium carbonate, calcium phosphate or kaolin, or as soft gelatin capsules wherein the active ingredient is mixed with water or an oil medium, for example peanut oil, liquid paraffin or olive oil.

Aqueous suspensions contain the active materials in admixture with excipients suitable for the manufacture of aqueous suspensions. Such excipients are suspending agents, for example sodium carboxymethylcellulose, methylcellulose, hydroxypropyl methylcellulose, sodium alginate, polyvinylpyrrolidone, gum tragacanth and gum acacia; dispersing or wetting agents may be a naturally occurring phosphatide, for example, lecithin, or condensation products or an alkylene oxide with fatty acids, for example polyoxyethylene stearate, or condensation products of ethylene oxide with long chain aliphatic alcohols, for example heptadecaethylene oxycetanol, or condensation products of ethylene oxide with partial esters derived from fatty acids and hexitol such as polyoxyethylene sorbitol monooleate, or condensation products of ethylene oxide with partial esters derived from fatty acids and hexitol anhydrides, for example polyethylene sorbitan monooleate. The aqueous suspensions may also contain one or more preservatives, for example ethyl, or n-propyl p-hydroxybenzoate, one or more coloring agents, one or more flavoring agents, and one or more sweetening agents, such as sucrose or saccharin.

Dispersible powders and granules suitable for preparation of an aqueous suspension by the addition of water provide the active ingredient in admixture with a dispersing or wetting agent, suspending agent and one or more preservatives. Suitable dispersing or wetting agents and suspending agents are exemplified by those already mentioned above. Additional excipients, for example, sweetening, flavoring and coloring agents, may also be present.

The compounds may also be in the form of non-aqueous liquid formulations, e.g., oily suspensions which may be formulated by suspending the active ingredients in a vegetable oil, for example arachis oil, olive oil, sesame oil or peanut oil, or in a mineral oil such as liquid paraffin. The oily suspensions may contain a thickening agent, for example beeswax, hard paraffin or cetyl alcohol. Sweetening agents such as those set forth above, and flavoring agents may be added to provide palatable oral preparations. These compositions may be preserved by the addition of an anti-oxidant such as ascorbic acid.

Pharmaceutical compositions of the invention may also be in the form of oil-in-water emulsions. The oily phase may be a vegetable oil, for example olive oil or arachis oil, or a mineral oil, for example liquid paraffin or mixtures of these. Suitable emulsifying agents may be naturally-occurring gums, for example gum acacia or gum tragacanth, naturally-occurring phosphatides, for example soy bean, lecithin, and esters or partial esters derived from fatty acids and hexitol anhydrides, for example sorbitan monooleate, and condensation products of the said partial esters with ethylene oxide, for example polyoxyethylene sorbitan monooleate. The emulsions may also contain sweetening and flavoring agents.

Syrups and elixirs may be formulated with sweetening agents, for example glycerol, propylene glycol, sorbitol or sucrose. Such formulations may also contain a demulcent, a preservative, and flavoring and coloring agents.

The compounds may also be administered in the form of suppositories for rectal administration of the drug. These compositions can be prepared by mixing the drug with a suitable non-irritating excipient which is solid at ordinary temperatures but liquid at the rectal temperature and will therefore melt in the rectum to release the drug. Such materials include cocoa butter and polyethylene glycols.

EXAMPLES

The following examples are representative of the compounds of the invention and methods for preparing them. However, the scope of the invention is not to be taken as being limited to these examples.

Synthetic Procedures

Starting materials not described explicitly were either available commercially or their synthesis has been described in the chemistry literature or the materials can be prepared by methods known to a person skilled in the art. Exemplar compounds were characterised by ¹H NMR spectroscopy, APCI ionisation mass spectrometry, melting point, and combustion or HRMS analysis. Purity of the exemplar compounds was determined by HPLC analysis and found to be >95% for all compounds.

Silica gel 60 (SiO₂) (0.040-0.063 mm) was used for all column chromatography.

Abbreviations

-   -   NMR nuclear magnetic resonance     -   ESI electrospray ionisation     -   APCI atmospheric pressure chemical ionisation     -   HPLC high performance liquid chromatography     -   LCMS liquid chromatography-mass spectrometry     -   HRMS high resolution mass spectrometry     -   mp melting point     -   DMF dimethylformamide     -   EtOAc ethyl acetate     -   DCM dichloromethane     -   MeOH methanol     -   THF tetrahydrofuran     -   HOAc acetic acid     -   dppf 2-(diphenylphosphino)ferrocene     -   EDCI 1-Ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride     -   TEA Triethylamine

Method 1. Representative Example 5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-amine (1)

To a solution of acetohydroxamic acid (0.22 g, 2.98 mmol) in dry DMF (5 ml) under nitrogen was added potassium tert-butoxide (0.33 g, 2.98 mmol). The reaction mixture was stirred at 20° C. for 2 hr. 2,5-Dichloro-4,6-dimethylnicotinonitrile (0.50 g, 2.49 mmol) was then added and the resulting mixture was stirred at 20° C. for 5 hr, then diluted with H₂O (150 ml) and stirred for 1 hr. The resulting white precipitate was filtered and washed with water. The filtrate was extracted with EtOAc (30 ml×3). Combined organic fractions were dried (Na₂SO₄), and the solvent was evaporated under vacuum to give further material. Both the isolated solid and the extracted material were combined and chromatographed on SiO₂ eluting with a 0-50% gradient of petroleum ether/EtOAc. The column purified product was recrystallized from DCM/petroleum ether to give (1) (0.22 g, 45%) as a white solid, mp (DCM/petroleum ether) 214-216° C., 1H NMR [(CD₃)₂SO] δ 6.25 (bs, 2H, NH₂), 2.64 (s, 3H, CH₃), 2.61 (s, 3H, CH₃); LCMS [M+H]=198; HPLC 99.8%; Anal calcd. for C₈H₈ClN₃O: C, 48.6; H, 4.1; N, 21.4. found C, 48.8; H, 3.9, N, 21.4%.

Method 9. Representative Procedure and Further Example Method 9. Representative Procedure 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-(trifluoromethoxy)phenyl)urea (2)

To a solution of 5-chloro-4,6-dimethylisoxazol[5,4-b)pyridine-3-amine (1) (125 mg, 0.60 mmol) in THF (1 ml) at 20° C. was added diisopropylethylamine (0.12 ml, 0.78 mmol, 1.3 eq) and 1-isocyanato-4-(trifluoromethoxy)benzene (0.1 ml, 0.74 mmol, 1.23 eq). The reaction mixture was stirred at this temperature for 72 hr, then quenched with aq. KHCO₃. The resulting precipitate was filtered and washed with H₂O. The filtrate was extracted with EtOAc to give further material after evaporation of the solvent. The combined solid material was triturated with diisopropyl ether for 3 days to give (2) (18 mg, 7%), mp (diisopropyl ether) 205-208° C.; 1H NMR [(CD₃)₂SO] δ 9.55 (s, 1H), 9.47 (s, 1H), 7.60 (d, J=9.1 Hz, 2H), 7.32 (d, J=9.1 Hz, 2H), 2.69 (s, 3H), 2.58 (s, 3H); HPLC purity 84%; HRMS (ESI⁺) calcd. for C₁₆H₁₂ClF₃N₄NaO₃ [M+Na] 423.0442, found 423.0440.

1-(5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-cyanophenyl)urea (3)

Similarly from 5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridine-3-amine and 4-isocyanatobenzonitrile to give (3) in 3.5% yield, mp (MeOH) 223-224° C.; 1H NMR [(CD₃)₂SO] δ 9.86 (s, 1H), 9.62 (s, 1H), 7.77 (d, J=8.9 Hz, 2H), 7.67 (d, J=8.9 Hz, 2H), 2.69 (s, 3H), 2.57 (s, 3H); Anal. calcd. for C₁₆H₁₂ClN₅O₂: C, 56.2; H, 3.5; N, 20.5. found C, 56.2; H, 3.4; N, 20.4%.

Method 10. Representative Example

General Procedure

To a solution of 1 (1.5 g, 7.6 mmol, 1.0 eq) and TEA (1.5 g, 15.2 mmol, 2.0 eq) in THF (200 mL) at 0° C. was added phenyl chloroformate B (1.2 g, 76 mmol, 10.0 eq) drop-wise with stirring. The reaction mixture was stirred at room temperature under a N₂ atmosphere overnight. The reaction mixture was poured into water and extracted with EtOAc (25 mL×3). The combined organic layers were washed with saturated aqueous NaHCO₃ solution and brine, dried over Na₂SO₄, filtered and concentrated. The residue was purified by column chromatography (pet. ether/EtOAc=10/1-5/1) to give the product 4 (1.7 g, 71%) as a white solid.

Similar reaction of 1 with 4-fluorophenyl chloroformate gave 5 as a white solid (64%) following chromatography on silica (pet. ether/EtOAc (1:1).

To a solution of 4 (0.47 mmol, 1.0 eq) in THF (8.0 mL) were added TEA (0.94 mmol, 2.0 eq) and substituted aniline D (0.71 mmol, 1.5 eq). The reaction mixture was stirred at room temperature under a N₂ atmosphere overnight. The reaction mixture was concentrated under reduced pressure, and the residue was purified by column chromatography (CH₂Cl₂/MeOH=100/1-80/1) to give the desired product.

The following compounds were prepared using the methods described above:

Compound Number Structure [M + H]⁺ ¹H NMR spectrum  4

317.8 319.8 1H NMR (400 MHz, DMSO & HCl) δ 11.08 (s, 1H), 7.39 (t, J = 7.6 Hz, 2H), 7.23 (t, J = 7.6 Hz, 1H), 7.17 (d, J = 7.6 Hz, 2H), 2.61 (s, 3H), 2.58 (s, 3H).  5

336.1 338.0 1H NMR (400 MHz, CDCl₃) δ 7.24 (br, 1H), 7.20-7.15 (m, 2H), 7.13-7.01 (m, 2H), 2.77 (s, 3H), 2.67 (s, 3H).  6

351.1 353.0 1H NMR (400 MHz, DMSO) δ 10.13 (s, 1H), 9.05 (s, 1H), 8.03 (d, J = 8.2 Hz, 1H), 7.50 (d, J = 8.0 Hz, 1H), 7.36-7.28 (m, 1H), 7.16-7.06 (m, 1H), 2.69 (s, 3H), 2.63 (s, 3H).  7

350.9 352.9 1H NMR (400 MHz, DMSO) δ 9.57 (s, 1H), 9.53 (s, 1H), 7.68 (t, J = 2.4 Hz, 1H), 7.38- 7.30 (m, 2H), 7.07 (dt, J₁ = 3.6 Hz, J₂ = 2.0 Hz, 1H), 2.68 (s, 3H), 2.57 (s, 3H).  8

351.0 353.0 1H NMR (400 MHz, DMSO) δ 9.82 (s, 1H), 9.63 (s, 1H), 7.51 (d, J = 8.8 Hz, 2H), 7.35 (d, J = 8.8 Hz, 2H), 2.68 (s, 3H), 2.60 (s, 3H).  9

401.1 403.1 1H NMR (400 MHz, DMSO) δ 9.76 (s, 1H), 9.07 (s, 1H), 8.11 (dd, J₁ = 8.4 Hz, J₂ = 1.2 Hz, 1H), 7.43 (d, J = 8.4 Hz, 1H), 7.38 (t, J = 8.0 Hz, 1H), 7.20 (t, J = 8.4 Hz, 1H), 2.70 (s, 3H), 2.61 (s, 3H). 10

401.1 403.1 1H NMR (400 MHz, DMSO) δ 9.67 (s, 1H), 9.52 (s, 1H), 7.64 (s, 1H), 7.43 (d, J = 5.9 Hz, 2H), 7.00 (d, J = 5.7 Hz, 1H), 2.69 (s, 3H), 2.58 (s, 3H). 11

347.1 349.1 1H NMR (400 MHz, DMSO) δ 9.73 (s, 1H), 8.81 (s, 1H), 8.03 (dd, J₁ = 8.0 Hz, J₂ = 1.2 Hz, 1H), 7.08-7.00 (m, 2H), 6.93-6.89 (m, 1H), 3.90 (s, 3H), 2.69 (s, 3H), 2.61 (s, 3H). 12

347.1 349.1 1H NMR (400 MHz, DMSO) δ 9.52 (s, 1H), 9.47 (s, 1H), 7.22-7.17 (m, 2H), 7.01 (d, J = 8.0 Hz, 1H), 6.61 (dd, J₁ = 8.1 Hz, J₂ = 2.1 Hz, 1H), 3.72 (s, 3H), 2.69 (s, 3H), 2.60 (s, 3H). 13

347.1 349.1 1H NMR (400 MHz, DMSO) δ 9.42 (s, 1H), 9.34 (s, 1H), 7.38 (d, J = 9.2 Hz, 2H), 6.88 (d, J = 8.8 Hz, 2H), 3.72 (s, 3H), 2.68 (s, 3H), 2.60 (s, 3H). 14

385.1 387.1 1H NMR (400 MHz, DMSO) δ 9.80 (s, 1H), 8.74 (s, 1H), 7.81 (d, J = 8.0 Hz, 1H), 7.74 (d, J = 8.0 Hz, 1H), 7.68 (t, J = 8.0 Hz, 1H), 7.38 (t, J = 7.6 Hz, 1H), 2.69 (s, 3H), 2.60 (s, 3H). 15

385.1 387.1 1H NMR (400 MHz, DMSO) δ 9.79 (s, 1H), 9.61 (s, 1H), 7.96 (s, 1H), 7.70 (d, J = 8.4 Hz, 1H), 7.55 (t, J = 8.0 Hz, 1H), 7.37 (d, J = 7.6 Hz, 1H), 2.69 (s, 3H), 2.58 (s, 3H). 16

385.0 387.1 1H NMR (400 MHz, DMSO) δ 9.84 (s, 1H), 9.58 (s, 1H), 7.68 (q, J = 8.8 Hz, 4H), 2.69 (s, 3H), 2.59 (s, 3H). 17

317.1 319.1 1H NMR (400 MHz, DMSO) δ 9.35 (s, 1H), 9.32 (s, 1H), 7.48 (d, J = 7.6 Hz, 2H), 7.31 (t, J = 7.6 Hz, 2H), 7.03 (t, J = 7.6 Hz, 1H), 2.69 (s, 3H), 2.59 (s, 3H).

Method 11. Representative Examples

General Experimental Conditions A

To a solution of a substituted phenylacetic acid (0.56 mmol, 1.1 eq) in CH₂Cl₂ (8.0 ml) was added oxalyl chloride (78 mg, 0.62 mmol, 1.2 eq). The resulting mixture was stirred at room temperature under N₂ for 2 h. The reaction mixture was concentrated under reduced pressure to afford acid chloride B, which was dissolved in THF (2 ml). The prepared acid chloride solution was added to a mixture of 1 (100 mg, 0.51 mmol, 1.0 eq) and NaH (24.8 mg, 0.62 mmol, 1.2 eq) in THF (5 ml) at 0° C., and the resulting mixture was stirred at 40° C. overnight. The reaction mixture was poured into water and extracted with EtOAc (25 mL×3). The organic layers were combined and washed with saturated aqueous NaHCO₃ solution and brine, then dried over Na₂SO₄, filtered and concentrated. The residue was purified by column chromatography (pet. ether/EtOAc=5/1-3/1) to give the desired product.

General Experimental Conditions B

To a solution of a substituted phenylacetic acid, or acetic acid (5.1 mmol, 10 eq) in CH₂Cl₂ (8.0 ml) was added oxalyl chloride (710 mg, 5.6 mmol, 11 eq) and DMF (2 drops, cat). The resulting mixture was stirred at room temperature under N₂ for 2 h. The reaction mixture was concentrated under reduced pressure to afford acid chloride B, which was dissolved in THF (2 ml). The prepared acyl chloride solution was added to a mixture of 1 (100 mg, 0.51 mmol, 1.0 eq) and TEA (103 mg, 1.02 mmol, 2.0 eq) in THF (5 ml) at 0° C., and the resulting mixture was stirred at RT overnight. The reaction mixture was poured into water and extracted with EtOAc (25 mL×3). The organic layers were combined and washed with saturated aqueous NaHCO₃ solution and brine, then dried over Na₂SO₄, filtered and concentrated. The residue was recrystallised from CH₂Cl₂ to give the desired product.

The following compounds were prepared using the methods described above:

Compound Preparation Number Structure [M + H]⁺ ¹H NMR method 18

315.9 317.8 1H NMR (400 MHz, DMSO) δ 12.30 (s, 1H), 7.38 (d, J = 4.4 Hz, 5H), 4.42 (s, 2H), 2.34 (s, 3H), 2.06 (s, 3H). A 19

400.1 402.1 1H NMR (400 MHz, CD₃OD) δ 7.49 (d, J = 8.4 Hz, 2H), 7.27 (d, J = 8.0 Hz, 2H), 3.86 (s, 2H), 2.70 (s, 3H), 2.35 (s, 3H). B 20

240.1 242.1 1H NMR (400 MHz, CDCl₃) δ 7.67 (br, 1H), 2.75 (s, 3H), 2.58 (br s, 3H), 2.34 (br s, 3H). B

Enzymatic Assay for IDO1 Activity

Recombinant human IDO1 (rhIDO1) was expressed and purified from cultures of EC538 strain of E. coli transformed with pREP4 and pQE9-IDO plasmid. Reaction mixes were set up in 384-well microplates containing 50 mM phosphate buffer, 10 mM ascorbic, 10 μM methylene blue, 100 μg/mL catalase, 80 μM TRP, 0.01% Tween 20 (v/v) mixed with rhIDO1 (15 μL) at a final concentration of 9 nM in a total volume of 30 μL assay medium. The plates were incubated at 37° C. for 30 min, and the enzymatic reaction was terminated by adding piperidine (200 mM) and heated at 65° C. for 20 min. Fluorescence intensity was read at λ_(ex) 400 nm and λ_(em) 500 nm. Test compounds were dissolved in 100% DMSO and pre-diluted in assay medium prior to adding rhIDO1. IDO1 inhibition (%) was calculated as

$\left( {\frac{\left( {{❘{{uninhibited}{enzyme}{assay}{signal}}❘} - {❘{{inhibited}{enzyme}{signal}}❘}} \right)}{\left( {{❘{{uninhibited}{enzyme}{assay}{signal}}❘} - {❘{{assay}{medium}{signal}}❘}} \right)} \times 100} \right)$

All experiments were carried out in triplicates, and statistical Analyses were conducted in Prism v5 (Graphpad Software, Inc., La Jolla, Calif., USA).

Cell-Based Assay for IDO1 Inhibition

For the assay of inhibition of cellular IDO1 activity, Lewis Lung carcinoma cells transfected to express human IDO1 (LLTC-hIDO1) or murine (LLTC-mIDO1) were cultured with test compounds at 37° C., 5% CO₂ for 24 h. Culture supernatant from each well was then transferred into a fresh, flat-bottomed 96-well plate, mixed with trichloroacetic acid (10% final concentration) and incubated for 20 min at 60° C. Plates were then centrifuged (10 min at 2500 g) and the supernatants were then transferred and mixed 1:1 with 4-(dimethylamino)benzaldehyde (20 mg/mL in acetic acid) in a new plate. The absorbance of each well was read at 480 nm, and the concentration that inhibited 50% cellular enzyme activity was calculated.

The viability of the cells in each well in the same experiment was determined using the 3-(4,5-dimethylthiazolyl-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colourimetric assay. After the removal of the supernatant for determination of IDO1 inhibition, the cells were incubated with MTT (500 μg/mL) until crystal formation was observed. Plates were centrifuged for 15 min at 2500 g, and then all the supernatant in then wells was discarded. DMSO (100 μL/well) was added to dissolve the crystals and then the absorbance in each well was measured at 570 nm. Cell viability in each well was expressed as a percentage of untreated controls. Triplicate cultures were used for all experiments unless stated otherwise.

Results of the assays are shown in the table below.

Compound Activity

Enzymatic Cellular Cell cytotoxicity Compound No IC₅₀ IC₅₀ IC₅₀ 1 B A D 2 D C D 3 C A D 4 B A D 6 D B D 7 D B D 8 D B D 9 D B D 10 D B D 11 C B D 12 D B D 13 D B D 14 D C D 15 D B D 16 D B D 17 C B D 18 D — — 19 D B D 20 D D D Activity IC₅₀ ranges: A; <1 μM, B; 1-10 μM, C; 10-100 μM, D; >100 μM

Cell-Based Assay for TDO Inhibition

For the assay of inhibition of cellular TDO, GL261 cells transfected to over-express full length human TDO were cultured with test compounds at 37° C., 5% CO₂ for 24 h. Culture supernatant from each well was then transferred into a fresh, flat-bottomed 96-well plate, and kynurenine content was determined as described above for the IDO1 assay, and the concentration that inhibited 50% cellular enzyme activity was calculated.

The viability of the cells in each well in the same experiment was determined using the 3-(4,5-dimethylthiazolyl-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colourimetric assay.

Results of the assay are shown in the table below.

Compound Activity

Cellular Cell cytotoxicity Compound No IC₅₀ IC₅₀ 1 B D 4 C D 15 C D Activity IC₅₀ ranges: A; <1 μM, B; 1-10 μM, C; 10-100 μM, D; >100 μM

As used herein, “comprising” is synonymous with “including,” “containing,” or “characterized by,” and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, “consisting of” excludes any element, step, or ingredient not specified in the claim element. As used herein, “consisting essentially of” does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. In each instance herein any of the terms “comprising”, “consisting essentially of” and “consisting of” may be replaced with either of the other two terms.

When a group of materials, compositions, components or compounds is disclosed herein, it is understood that all individual members of those groups and all subgroups thereof are disclosed separately. When a Markush group or other grouping is used herein, all individual members of the group and all combinations and subcombinations possible of the group are intended to be individually included in the disclosure. Every formulation or combination of components described or exemplified herein can be used to practice the invention, unless otherwise stated. Whenever a range is given in the specification, for example, a temperature range, a time range, or a composition range, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure. In the disclosure and the claims, “and/or” means additionally or alternatively. Moreover, any use of a term in the singular also encompasses plural forms.

All references cited herein are hereby incorporated by reference in their entirety to the extent that there is no inconsistency with the disclosure of this specification. Some references provided herein are incorporated by reference to provide details concerning sources of starting materials, additional starting materials, additional reagents, additional methods of synthesis, additional methods of analysis, additional biological materials, additional cells, and additional uses of the invention. All headings used herein are for convenience only. All patents and publications mentioned in the specification are indicative of the levels of skill of those skilled in the art to which the invention pertains, and are herein incorporated by reference to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference. References cited herein are incorporated by reference herein in their entirety to indicate the state of the art as of their publication or filing date and it is intended that this information can be employed herein, if needed, to exclude specific embodiments that are in the prior art. 

1. A pharmaceutical composition comprising: a compound of Formula I or a pharmaceutically acceptable salt thereof, wherein:

W is CR¹, N or N-oxide; X is CR², N or N-oxide; Y is CR³, N or N-oxide; Z is CR⁴, N or N-oxide; and where at least one of W, X, Y, and Z is N or N-oxide; R¹, R², R³ and R⁴ are each independently selected from the following groups: H, halo, R, —OH, —OR, —OC(O)H, —OC(O)R, —OC(O)NH₂, —OC(O)NHR, —OC(O)NRR, —OP(O)(OH)₂, —OP(O)(OR)₂, —NO₂, —NH₂, —NHR, —NRR, —NHC(O)H, —NHC(O)R, —NRC(O)R, —NHC(O)NH₂, —NHC(O)NRR, —NRC(O)NHR, —SH, —SR, —S(O)H, —S(O)R, —SO₂R, —SO₂NH₂, —SO₂NHR, —SO₂NRR, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —CN, —C≡CH, —C≡CR, —CH═CHR, —CH═CRR, —CR═CHR, —CR═CRR, —CO₂H, —CO₂R, —CHO, —C(O)R, —C(O)NH₂, —C(O)NHR, —C(O)NRR, —CONHSO₂H, —CONHSO₂R, —CONRSO₂R, cyclic C₃-C₇ alkylamino, imidazolyl, C₁-C₆ alkylpiperazinyl, morpholinyl and thiomorpholinyl; or R¹ and R² taken together, or R² and R³ taken together, or R³ and R⁴ taken together can form a saturated or a partially saturated or a fully unsaturated 5- or 6-membered ring of carbon atoms optionally including 1 to 3 heteroatoms selected from O, N and S, and the ring is optionally substituted independently with 1 to 4 substituents selected from R; each R is independently selected from any of the groups defined in paragraphs (a) and (b) below: (a) an optionally substituted C₁₋₆ alkyl group, an optionally substituted C₂₋₆ alkenyl group, an optionally substituted C₂₋₆ alkynyl group and an optionally substituted C₃₋₇ cyclic alkyl group; wherein the one or more optional substituents for each of said alkyl, alkenyl, alkynyl and cyclic alkyl groups are each independently selected from the following groups: halo, —OH, —OR⁵, —OC(O)R⁵, —OC(O)NH₂, —OC(O)NHR⁵, —OC(O)NR⁵R⁵, —OP(O)(OH)₂, —OP(O)(OR⁵)₂, —NO₂, —NH₂, —NHR⁵, —NR⁵R⁵, —N⁺(O⁻)R⁵R⁵, —NHC(O)H, —NHC(O)R⁵, —NR⁵C(O)R⁵, —NHC(O)NH₂, —NHC(O)NR⁵R⁵, —NR⁵C(O)NHR⁵, —SH, —SR⁵, —S(O)H, —S(O)R⁵, —SO₂R⁵, —SO₂NH₂, —SO₂NHR⁵, —SO₂NR⁵R⁵, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —CN, —CO₂H, —CO₂R⁵, —CHO, —C(O)R⁵, —C(O)NH₂, —C(O)NHR⁵, —C(O)NR⁵R⁵, —CONHSO₂H, —C(O)NHSO₂R⁵, —C(O)NR⁵SO₂R⁵, cyclic C₃-C₇ alkylamino, imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl and azetidinyl; wherein each of the groups imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl and azetidinyl are optionally substituted by one or more of the following groups: C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cyclic alkyl, halo, —OH, —OR⁷, —OC(O)R⁷, —OC(O)NH₂—OC(O)NHR⁷, —OC(O)NR⁷R⁷, —OP(O)(OH)₂, —OP(O)(OR⁷)₂, —NO₂, —NH₂, —NHR⁷, —NR⁷R⁷, —N⁺(O⁻) R⁷R⁷, —NHC(O)H, —NHC(O)R⁷, —NR⁷C(O)R⁷, —NHC(O)NH₂, —NHC(O)NR⁷R⁷, —NR⁷C(O)NHR⁷, —SH, —SR⁷, —S(O)H, —S(O)R⁷, —SO₂R⁷, —SO₂NH₂, —SO₂NHR⁷, —SO₂NR⁷R⁷, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R⁷, —CHO, —C(O)R⁷, —C(O)NH₂, —C(O)NHR⁷, —C(O)NR⁷R⁷, —CONHSO₂H, —C(O)NHSO₂R⁷, —C(O)NR⁷SO₂R⁷, an optionally substituted aryl, and an optionally substituted heteroaryl group having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; and wherein the one or more optional substituents for each of said aryl and heteroaryl groups are each independently selected from the following groups: C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₈ alkynyl or C₃₋₇ cyclic alkyl, halo, —OH, —OR⁸, —OC(O)R⁸, —OC(O)NH₂, —OC(O)NHR⁸, —OC(O)NR⁸R⁸, —OP(O)(OH)₂, —OP(O)(OR⁸)₂, —NO₂, —NH₂, —NHR⁸, —NR⁸R⁸, —N⁺(O)R⁸R⁸, —NHC(O)H, —NHC(O)R⁸, —NR⁸C(O)R⁸, —NHC(O)NH₂, —NHC(O)NR⁸R⁸, —NR⁸C(O)NHR⁸, —SH, —SR⁸, —S(O)H, —S(O)R⁸, —SO₂R⁸, —SO₂NH₂, —SO₂NHR⁸, —SO₂NR⁸R⁸, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R⁸, —CHO, —C(O)R⁸, —C(O)NH₂, —C(O)NHR⁸, —C(O)NR⁸R⁸, —CONHSO₂H, —C(O)NHSO₂R⁸, and —C(O)NR⁸SO₂R⁸; wherein each R⁵, R⁷ and R⁸ is independently selected from a C₁₋₆ alkyl group, a C₂₋₆ alkenyl group, a C₂₋₆ alkynyl group and a C₃₋₇ cyclic alkyl group; and (b) an optionally substituted aryl, and an optionally substituted heteroaryl group having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; and wherein the one or more optional substituents are each independently selected from the same optional substituents as those defined in (a) above for R; R⁹ and R¹⁰ are each independently selected from any of the groups defined in paragraphs (a) to (d) below, with the proviso that at least one of R⁹ and R¹⁰ is selected from any of the groups defined in paragraphs (c) and (d) below: (a) H, an optionally substituted C₁₋₆ alkyl group, an optionally substituted C₂₋₆ alkenyl group, an optionally substituted C₂₋₆ alkynyl group, and an optionally substituted C₃₋₇ cyclic alkyl group; wherein the one or more optional substituents for each of said alkyl, alkenyl, alkynyl and cyclic alkyl are each independently selected from the following groups: halo, —OH, —OR¹¹, —OC(O)R¹¹, —OC(O)NH₂, —OC(O)NHR¹¹, —OC(O)NR¹¹R¹¹, —OP(O)(OH)₂, —OP(O)(OR¹¹)₂, —NO₂, —NH₂, —NHR¹¹, —NR¹¹R¹¹, —N⁺(O)R¹¹R¹¹, —NHC(O)H, —NHC(O)R¹¹, —NR¹¹C(O)R¹¹, —NHC(O)NH₂, —NHC(O)NR¹¹R¹¹, —NR¹¹C(O)NHR¹¹, —SH, —SR¹¹, —S(O)H, —S(O)R¹¹, —SO₂R¹¹, —SO₂NH₂, —SO₂NHR¹¹, —SO₂NR¹¹R¹¹, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R¹¹, —CHO, —C(O)R¹¹, —C(O)NH₂, —C(O)NHR¹¹, —C(O)NR¹¹R¹¹, —CONHSO₂H, —C(O)NHSO₂R¹¹, —C(O)NR¹¹SO₂R¹¹, cyclic C₃-C₇ alkylamino, imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl, azetidinyl, aryl, and heteroaryl having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; wherein each of the groups cyclic C₃-C₇ alkylamino, imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl azetidinyl, aryl and heteroaryl are optionally substituted by one or more of the following groups: C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cyclic alkyl, halo, —OH, —OR¹³, —OC(O)R¹³, —OC(O)NH₂, —OC(O)NHR¹³, —OC(O)NR¹³R¹³, —OP(O)(OH)₂, —OP(O)(OR¹³)₂, —NO₂, —NH₂, —NHR¹³, —NR¹³R¹³, —N⁺(O)R¹³R¹³, —NHC(O)H, —NHC(O)R¹³, —NR¹³C(O)R¹³, —NHC(O)NH₂, —NHC(O)NR¹³R¹³, —NR¹³C(O)NHR¹³, —SH, —SR¹³, —S(O)H, —S(O)R¹³, —SO₂R¹³, —SO₂NH₂, —SO₂NHR¹³, —SO₂NR¹³R¹³, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R¹³, —CHO, —C(O)R¹³, —C(O)NH₂, —C(O)NHR¹³, —C(O)NR¹³R¹³, —CONHSO₂H, —C(O)NHSO₂R¹³, and —C(O)NR¹³SO₂R¹³; wherein each R¹¹ and R¹³ is independently selected from a C₁₋₆ alkyl group, a C₂₋₆ alkenyl group, a C₂₋₆ alkynyl group and a C₃₋₇ cyclic alkyl group; (b) an optionally substituted aryl, and an optionally substituted heteroaryl group having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; and wherein the one or more optional substituents for each of said aryl and heteroaryl are each independently selected from the same optional substituents as those defined in (a) above for R⁹ and R¹⁰; (c) —C(O)R¹⁴, —C(O)OR¹⁴, —C(O)NR¹⁵R¹⁶, —C(O)SR¹⁴, —C(S)R¹⁴, —C(S)OR¹⁴ C(S)NR¹⁵R¹⁶, and —C(S)SR¹⁴, wherein each R¹⁴ R¹⁵ and R¹⁶ is independently selected from the group consisting of H, optionally substituted C₁₋₆ alkyl, optionally substituted C₂₋₆ alkenyl, optionally substituted C₂₋₆ alkynyl, optionally substituted C₃₋₇ cyclic alkyl, optionally substituted aryl, and optionally substituted heteroaryl having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S, and wherein the one or more optional substituents for each of said alkyl, alkenyl, alkynyl, cyclic alkyl, aryl and heteroaryl for R¹⁴, R¹⁵ and R¹⁶ are each independently selected from the same optional substituents as those defined in (a) above for R⁹ and R¹⁰; and (d) —SO₂(CRR)_(n)R¹⁷, wherein n is an integer of from 0 to 6, each R is independently selected from the groups defined above for R, and R¹⁷ is optionally substituted aryl or optionally substituted heteroaryl having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S, and wherein the one or more optional substituents for each of said aryl and heteroaryl are independently selected from the same optional substituents as those defined in (a) above for R⁹ and R¹⁰; and —SO₂R¹⁸, wherein R¹⁸ is optionally substituted C₁₋₆ alkyl or optionally substituted C₃₋₇ cyclic alkyl, wherein the one or more optional substituents for each of said alkyl and cyclic alkyl are each independently selected from those defined in (a) above for R⁹ and R¹⁰; and a pharmaceutically acceptable carrier.
 2. A pharmaceutical composition according to claim 1, wherein (a) Z is N or N-oxide, such as N, W is CR¹, X is CR² and Y is CR³; or (b) X is N or N-oxide, such as N, W is CR¹, Y is CR³ and Z is CR⁴; or (c) X and Z are both N or N-oxide, such as N, W is CR¹ and Y is CR³. 3-4. (canceled)
 5. A pharmaceutical composition according to claim 1, wherein R¹, R², R³ and R⁴, where present, are each independently selected from the group consisting of H, halo, optionally substituted C₁-C₆ alkyl, —O—R wherein R is selected from optionally substituted C₁-C₆ alkyl and optionally substituted aryl (such as phenyl), —NHR wherein R is optionally substituted aryl, an optionally substituted aryl, and an optionally substituted heteroaryl group having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S.
 6. A pharmaceutical composition according to claim 5, wherein (a) R¹, R², R³ and R⁴, where present, are each independently selected from the group consisting of H, halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆ alkyl, such as methyl, substituted aryl, substituted heteroaryl, —OR wherein R is optionally substituted aryl, and —NHR wherein R is optionally substituted aryl; or (b) one or two of R¹, R², R³ and R⁴, where present, is H, and the others of R¹, R², R³ and R⁴ that are not H are independently selected from the group consisting of halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆ alkyl, such as methyl, substituted aryl, substituted heteroaryl, —OR wherein R is optionally substituted aryl, and —NHR wherein R is optionally substituted aryl.
 7. (canceled)
 8. A pharmaceutical composition according to claim 5, wherein R³ is present and selected from the group consisting of halogen, —OR wherein R is optionally substituted aryl, and —NHR wherein R is optionally substituted aryl.
 9. A pharmaceutical composition according to claim 2, wherein: (a) Z is N or N-oxide, such as N, W is CR¹, X is CR² and Y is CR³, and R³ is selected from the group consisting of halogen, —O—R wherein R is optionally substituted aryl, and —NHR wherein R is optionally substituted aryl; or (b) Z is N or N-oxide, such as N, W is CR¹, X is CR² and Y is CR³, R¹ is H, and one or both of R² and R³ are other than H, for example, both R² and R³ are other than H, or R² is H and R³ is other than H, or R³ is H and R² is other than H.
 10. (canceled)
 11. A pharmaceutical composition according to claim 9, wherein Z is N or N-oxide, such as N, W is CR¹, X is CR² and Y is CR³, R¹ is H, and one or both of R² and R³ are other than H, for example, both R² and R³ are other than H, or R² is H and R³ is other than H, or R³ is H and R² is other than H; and each of R² and R³ that is other than H is independently selected from the group consisting of halogen, optionally substituted C₁-C₆ alkyl, —OR wherein R is selected from optionally substituted C₁-C₆ alkyl and optionally substituted aryl, —NHR wherein R is optionally substituted aryl; an optionally substituted aryl, such as substituted phenyl, and an optionally substituted heteroaryl group.
 12. A pharmaceutical composition according to claim 11, wherein each of R² and R³ that is other than H is independently selected from the group consisting of halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆ alkyl such as methyl, substituted aryl, substituted heteroaryl, —OR wherein R is optionally substituted aryl, and —NHR wherein R is optionally substituted aryl.
 13. (canceled)
 14. A pharmaceutical composition according to claim 1, wherein one of R⁹ and R¹⁰ is selected from the group consisting of H and optionally substituted C₁₋₆ alkyl (such as C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is selected from any of the groups defined in paragraphs (c) and (d); or (b) one of R⁹ and R¹⁰ is selected from the group consisting of H and optionally substituted C₁₋₆ alkyl (such as C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is selected from any of the groups defined in paragraph (c); or (c) one of R⁹ and R¹⁰ is selected from the group consisting of H and optionally substituted C₁₋₆ alkyl (such as C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is selected from the group consisting of —C(O)R¹⁴, —C(O)OR¹⁴, —C(S)R¹⁴, and —C(S)OR¹⁴; wherein each R¹⁴ is independently selected from the group consisting of: (a) optionally substituted C₁₋₆ alkyl, for example C₁₋₆ alkyl wherein said alkyl is substituted by aryl and optionally one or two further substituents, and wherein said aryl is itself optionally substituted, and (b) optionally substituted aryl. 15-16. (canceled)
 17. A pharmaceutical composition according to claim 14, wherein one of R⁹ and R¹⁰ is selected from the group consisting of H and optionally substituted C₁₋₆ alkyl (such as C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is selected from the group consisting of —C(O)R¹⁴, —C(O)OR¹⁴, —C(S)R¹⁴, and —C(S)OR¹⁴; wherein each R¹⁴ is independently selected from the group consisting of: (a) optionally substituted C₁₋₆ alkyl, for example C₁₋₆ alkyl wherein said alkyl is substituted by aryl and optionally one or two further substituents, and wherein said aryl is itself optionally substituted, and (b) optionally substituted aryl; where each R¹⁴ is optionally substituted alkyl having the formula —(CH₂)_(n)(aryl), wherein n is an integer from 0 to 3, such as 0 or 1, and said aryl is optionally substituted.
 18. A pharmaceutical composition according to claim 14, wherein: one of R⁹ and R¹⁰ is selected from the group consisting of H and optionally substituted C₁₋₆ alkyl (such as C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is selected from any of the groups defined in paragraph (c), or one of R⁹ and R¹⁰ is selected from the group consisting of H and optionally substituted C₁₋₆ alkyl (such as C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is selected from the group consisting of —C(O)R¹⁴, —C(O)OR¹⁴, —C(S)R¹⁴, and —C(S)OR¹⁴; wherein each R¹⁴ is independently selected from the group consisting of: (a) optionally substituted C₁₋₆ alkyl, for example C₁₋₆ alkyl wherein said alkyl is substituted by aryl and optionally one or two further substituents, and wherein said aryl is itself optionally substituted, and (b) optionally substituted aryl; and one of R⁹ and R¹⁰ is selected from the group consisting of H and optionally substituted C₁₋₆ alkyl (such as C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is —C(O)OR¹⁴.
 19. A pharmaceutical composition according to claim 1, wherein one of R⁹ and R¹⁰ is selected from the group consisting of H and optionally substituted C₁₋₆ alkyl (such as C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is selected from the group consisting of —C(O)NR¹⁵R¹⁶ and —C(S)NR¹⁵R¹⁶, wherein each R¹⁵ and R¹⁶ is independently selected from the group consisting of (a) H, (b) optionally substituted C₁₋₆ alkyl, for example C₁₋₆ alkyl wherein said alkyl is substituted by aryl and, optionally, one or two further substituents, and wherein said aryl is itself optionally substituted, and (c) optionally substituted aryl.
 20. A pharmaceutical composition according to claim 19, wherein each R¹⁵ and R¹⁶ is independently selected from the group consisting of (a) H and (b) optionally substituted alkyl having the formula —(CH₂)_(n)(aryl), wherein n is an integer from 0 to 3, such as 0 or 1, and said aryl is optionally substituted.
 21. A pharmaceutical composition according to claim 19, wherein one but not both of R¹⁵ and R¹⁶ is H.
 22. A pharmaceutical composition according to claim 2, wherein Z is N or N-oxide, such as N, W is CR¹, X is CR² and Y is CR³, one of R⁹ and R¹⁰ is selected from the group consisting of H and optionally substituted C₁₋₆ alkyl (such as C₁₋₃ alkyl), and the other of R⁹ and R¹⁰ is —C(O)OR¹⁴, wherein each R¹⁴ is independently selected from the group consisting of: (a) optionally substituted C₁₋₆ alkyl, for example C₁₋₆ alkyl wherein said alkyl is substituted by aryl and, optionally, one or two further substituents, and wherein said aryl is itself optionally substituted, and (b) optionally substituted aryl.
 23. A pharmaceutical composition according to claim 22, wherein R¹⁴ is optionally substituted alkyl having the formula —(CH₂)_(n)(aryl), wherein n is an integer from 0 to 3, such as 0 or 1, and said aryl is optionally substituted.
 24. A pharmaceutical composition according to claim 22, wherein (a) R¹, R² and R³ are each independently selected from the group consisting of H, halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆ alkyl, such as methyl, substituted aryl, substituted heteroaryl, —OR wherein R is optionally substituted aryl, and —NHR wherein R is optionally substituted aryl; or (b) R¹, R² and R³ are each independently selected from the group consisting of H, halogen, C₁₋₆ alkyl, such as methyl, substituted aryl, and substituted heteroaryl; or (c) one or two of R¹, R² and R³ is H, and the others of R¹, R² and R³ that are not H are independently selected from the group consisting of halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆ alkyl, such as methyl, substituted aryl, substituted heteroaryl, —OR wherein R is optionally substituted aryl, and —NHR wherein R is optionally substituted aryl; or (d) R¹ is H, and one of both of R² and R³ is other than H, wherein each of R² and R³ that is not H is independently selected from the group consisting of halogen, —CF₃, —CHF₂, —OCF₃, —OCHF₂, C₁₋₆ alkyl, such as methyl, substituted aryl, substituted heteroaryl, —OR wherein R is optionally substituted aryl, and —NHR wherein R is optionally substituted aryl. 25-27. (canceled)
 28. A pharmaceutical composition according to claim 22, wherein R³ is selected from the group consisting of halogen, —OR wherein R is optionally substituted aryl, and —NHR wherein R is optionally substituted aryl.
 29. (canceled)
 30. A pharmaceutical composition according to claim 1, wherein the compound of formula 1 is selected from the group consisting of: 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-(trifluoromethoxy)phenyl)urea (2) 1-(5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-cyanophenyl)urea (3) 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(2-chlorophenyl)urea (6) 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(3-chlorophenyl)urea (7) 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-chlorophenyl)urea (8) 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(2-(trifluoromethoxy)phenyl)urea (9) 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(3-(trifluoromethoxy)phenyl)urea (10) 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(2-methoxyphenyl)urea (11) 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(3-methoxyphenyl)urea (12) 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-methoxyphenyl)urea (13) 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(2-(trifluoromethyl)phenyl)urea (14) 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(4-(trifluoromethyl)phenyl)urea (16) 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-phenylurea (17) N-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-2-phenylacetamide (18) N-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-2-(4-(trifluoromethoxy)phenyl)acetamide (19) Phenyl (5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)carbamate (4) 1-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)-3-(3-(trifluoromethyl)phenyl)urea (15) 4-Fluorophenyl (5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)carbamate (5) N-(5-Chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)acetamide (20) and pharmaceutically acceptable salts thereof. 31-33. (canceled)
 34. A compound of Formula I or a pharmaceutically acceptable salt thereof, wherein:

W is CR¹, N or N-oxide; X is CR², N or N-oxide; Y is CR³, N or N-oxide; Z is CR⁴, N or N-oxide; and where at least one of W, X, Y, and Z is N or N-oxide; R¹, R², R³ and R⁴ are each independently selected from the following groups: H, halo, R, —OH, —OR, —OC(O)H, —OC(O)R, —OC(O)NH₂, —OC(O)NHR, —OC(O)NRR, —OP(O)(OH)₂, —OP(O)(OR)₂, —NO₂, —NH₂, —NHR, —NRR, —NHC(O)H, —NHC(O)R, —NRC(O)R, —NHC(O)NH₂, —NHC(O)NRR, —NRC(O)NHR, —SH, —SR, —S(O)H, —S(O)R, —SO₂R, —SO₂NH₂, —SO₂NHR, —SO₂NRR, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —CN, —C═CH, —C═CR, —CH═CHR, —CH═CRR, —CR═CHR, —CR═CRR, —CO₂H, —CO₂R, —CHO, —C(O)R, —C(O)NH₂, —C(O)NHR, —C(O)NRR, —CONHSO₂H, —CONHSO₂R, —CONRSO₂R, cyclic C₃-C₇ alkylamino, imidazolyl, C₁-C₆-alkylpiperazinyl, morpholinyl and thiomorpholinyl; or R¹ and R² taken together, or R² and R³ taken together, or R³ and R⁴ taken together can form a saturated or a partially saturated or a fully unsaturated 5- or 6-membered ring of carbon atoms optionally including 1 to 3 heteroatoms selected from O, N and S, and the ring is optionally substituted independently with 1 to 4 substituents selected from R; each R is independently selected from any of the groups defined in paragraphs (a) and (b) below: (a) an optionally substituted C₁₋₆ alkyl group, an optionally substituted C₂₋₆ alkenyl group, an optionally substituted C₂₋₆ alkynyl group and an optionally substituted C₃₋₇ cyclic alkyl group; wherein the one or more optional substituents for each of said alkyl, alkenyl, alkynyl and cyclic alkyl groups are each independently selected from the following groups: halo, —OH, —OR⁵, —OC(O)R⁵, —OC(O)NH₂, —OC(O)NHR⁵, —OC(O)NR⁵R⁵, —OP(O)(OH)₂, —OP(O)(OR⁵)₂, —NO₂, —NH₂, —NHR⁵, —NR⁵R⁵, —N⁺(O⁻)R⁵R⁵, —NHC(O)H, —NHC(O)R⁵, —NR⁵C(O)R⁵, —NHC(O)NH₂, —NHC(O)NR⁵R⁵, —NR⁵C(O)NHR⁵, —SH, —SR⁵, —S(O)H, —S(O)R⁵, —SO₂R⁵, —SO₂NH₂, —SO₂NHR⁵, —SO₂NR⁵R⁵, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —CN, —CO₂H, —CO₂R⁵, —CHO, —C(O)R⁵, —C(O)NH₂, —C(O)NHR⁵, —C(O)NR⁵R⁵, —CONHSO₂H, —C(O)NHSO₂R⁵, —C(O)NR⁵SO₂R⁵, cyclic C₃-C₇ alkylamino, imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl and azetidinyl; wherein each of the groups imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl and azetidinyl are optionally substituted by one or more of the following groups: C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cyclic alkyl, halo, —OH, —OR⁷, —OC(O)R⁷, —OC(O)NH₂—OC(O)NHR⁷, —OC(O)NR⁷R⁷, —OP(O)(OH)₂, —OP(O)(OR⁷)₂, —NO₂, —NH₂, —NHR⁷, —NR⁷R⁷, —N⁺(O⁻) R⁷R⁷, —NHC(O)H, —NHC(O)R⁷, —NR⁷C(O)R⁷, —NHC(O)NH₂, —NHC(O)NR⁷R⁷, —NR⁷C(O)NHR⁷, —SH, —SR⁷, —S(O)H, —S(O)R⁷, —SO₂R⁷, —SO₂NH₂, —SO₂NHR⁷, —SO₂NR⁷R⁷, —CF₃, —CHF₂, —CH₂F, —OCF₃, OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R⁷, —CHO, —C(O)R⁷, —C(O)NH₂, —C(O)NHR⁷, —C(O)NR⁷R⁷, —CONHSO₂H, —C(O)NHSO₂R⁷, —C(O)NR⁷SO₂R⁷, an optionally substituted aryl, and an optionally substituted heteroaryl group having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; and wherein the one or more optional substituents for each of said aryl and heteroaryl groups are each independently selected from the following groups: C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl or C₃₋₇ cyclic alkyl, halo, —OH, —OR⁸, —OC(O)R⁸, —OC(O)NH₂, —OC(O)NHR⁸, —OC(O)NR⁸R⁸, —OP(O)(OH)₂, —OP(O)(OR⁸)₂, —NO₂, —NH₂, —NHR⁸, —NR⁸R⁸, —N⁺(O)R⁸R⁸, —NHC(O)H, —NHC(O)R⁸, —NR³C(O)R⁸, —NHC(O)NH₂, —NHC(O)NR⁸R⁸, —NR⁸C(O)NHR⁸, —SH, —SR⁸, —S(O)H, —S(O)R⁸, —SO₂R⁸, —SO₂NH₂, —SO₂NHR⁸, —SO₂NR⁸R⁸, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R⁸, —CHO, —C(O)R⁸, —C(O)NH₂, —C(O)NHR⁸, —C(O)NR⁸R⁸, —CONHSO₂H, —C(O)NHSO₂R⁸, and —C(O)NR⁸SO₂R⁸; wherein each R⁵, R⁷ and R⁸ is independently selected from a C₁₋₆ alkyl group, a C₂₋₆ alkenyl group, a C₂₋₆ alkynyl group and a C₃₋₇ cyclic alkyl group; and (b) an optionally substituted aryl, and an optionally substituted heteroaryl group having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; and wherein the one or more optional substituents are each independently selected from the same optional substituents as those defined in (a) above for R; R⁹ and R¹⁰ are each independently selected from any of the groups defined in paragraphs (a) to (d) below, with the proviso that at least one of R⁹ and R¹⁰ is selected from any of the groups defined in paragraphs (c) and (d) below: (a) H, an optionally substituted C₁₋₆ alkyl group, an optionally substituted C₂₋₆ alkenyl group, an optionally substituted C₂₋₆ alkynyl group, and an optionally substituted C₃₋₇ cyclic alkyl group; wherein the one or more optional substituents for each of said alkyl, alkenyl, alkynyl and cyclic alkyl are each independently selected from the following groups: halo, —OH, —OR¹¹, —OC(O)R¹¹, —OC(O)NH₂, —OC(O)NHR¹¹, —OC(O)NR¹¹R¹¹, —OP(O)(OH)₂, —OP(O)(OR¹¹)₂, —NO₂, —NH₂, —NHR¹¹, —NR¹¹R¹¹, —N⁺(O)R¹¹R¹¹, —NHC(O)H, —NHC(O)R¹¹, —NR¹¹C(O)R¹¹, —NHC(O)NH₂, —NHC(O)NR¹¹R¹¹, —NR¹¹C(O)NHR¹¹, —SH, —SR¹¹, —S(O)H, —S(O)R¹¹, —SO₂R¹¹, —SO₂NH₂, —SO₂NHR¹¹, —SO₂NR¹¹R¹¹, —CF₃, —CHF₂, —CH₂F, —OCF₃, —OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R¹¹, —CHO, —C(O)R¹¹, —C(O)NH₂, —C(O)NHR¹¹, —C(O)NR¹¹R¹¹, —CONHSO₂H, —C(O)NHSO₂R¹¹, —C(O)NR¹¹SO₂R¹¹, cyclic C₃-C₇ alkylamino, imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl, azetidinyl, aryl, and heteroaryl having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; wherein each of the groups cyclic C₃-C₇ alkylamino, imidazolyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl, azepanyl, pyrrolidinyl azetidinyl, aryl and heteroaryl are optionally substituted by one or more of the following groups: C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cyclic alkyl, halo, —OH, —OR¹³, —OC(O)R¹³, —OC(O)NH₂, —OC(O)NHR¹³, —OC(O)NR¹³R¹³, —OP(O)(OH)₂, —OP(O)(OR¹³)₂, —NO₂, —NH₂, —NHR¹³, —NR¹³R¹³, —N⁺(O)R¹³R¹³, —NHC(O)H, —NHC(O)R¹³, —NR¹³C(O)R¹³, —NHC(O)NH₂, —NHC(O)NR¹³R¹³, —NR¹³C(O)NHR¹³, —SH, —SR¹³, —S(O)H, —S(O)R¹³, —SO₂R¹³, —SO₂NH₂, —SO₂NHR¹³, —SO₂NR¹³R¹³, —CF₃, —CHF₂, —CH₂F, —OCF₃, OCHF₂, —SCF₃, —SCF₂H, —CN, —CO₂H, —CO₂R¹³, —CHO, —C(O)R¹³, —C(O)NH₂, —C(O)NHR¹³, —C(O)NR¹³R¹³, —CONHSO₂H, —C(O)NHSO₂R¹³, and —C(O)NR¹³SO₂R¹³; wherein each R¹¹ and R¹³ is independently selected from a C₁₋₆ alkyl group, a C₂₋₆ alkenyl group, a C₂₋₆ alkynyl group and a C₃₋₇ cyclic alkyl group; (b) an optionally substituted aryl, and an optionally substituted heteroaryl group having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S; and wherein the one or more optional substituents for each of said aryl and heteroaryl are each independently selected from the same optional substituents as those defined in (a) above for R⁹ and R¹⁰; (c) —C(O)R¹⁴, —C(O)OR¹⁴, —C(O)NR¹⁵R¹⁶, —C(O)SR¹⁴, —C(S)R¹⁴, —C(S)OR¹⁴ C(S)NR¹⁵R¹⁶, and —C(S)SR¹⁴, wherein each R¹⁴, R¹⁵ and R¹⁶ is independently selected from the group consisting of H, optionally substituted C₁₋₆ alkyl, optionally substituted C₂₋₆ alkenyl, optionally substituted C₂₋₆ alkynyl, optionally substituted C₃₋₇ cyclic alkyl, optionally substituted aryl, and optionally substituted heteroaryl having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S, and wherein the one or more optional substituents for each of said alkyl, alkenyl, alkynyl, cyclic alkyl, aryl and heteroaryl for R¹⁴, R¹⁵ and R¹⁶ are each independently selected from the same optional substituents as those defined in (a) above for R⁹ and R¹⁰; and (d) —SO₂(CRR)_(n)R¹⁷, wherein n is an integer of from 0 to 6, each R is independently selected from the groups defined above for R, and R¹⁷ is optionally substituted aryl or optionally substituted heteroaryl having up to 12 carbon atoms and having one or more heteroatoms in its ring system which are each independently selected from O, N and S, and wherein the one or more optional substituents for each of said aryl and heteroaryl are independently selected from the same optional substituents as those defined in (a) above for R⁹ and R¹⁰; and —SO₂R¹⁸, wherein R¹⁸ is optionally substituted C₁₋₆alkyl or optionally substituted C₃₋₇ cyclic alkyl, wherein the one or more optional substituents for each of said alkyl and cyclic alkyl are each independently selected from those defined in (a) above for R⁹ and R¹⁰; with the proviso that at least one of R¹, R², R³ and R⁴, where present, is other than H or methyl, and with the further proviso that the compound is not selected from the following: 2-Bromo-N-(5-chloro-4,6-dimethylisoxazolo[5,4-b]pyridin-3-yl)acetamide, N-(6-Phenyl-4-(trifluoromethyl)isoxazolo[5,4-b]pyridin-3-yl)cyclopropanecarboxamide, and 2-Phenyl-N-(6-phenyl-4-(trifluoromethyl)isoxazolo[5,4-b]pyridin-3-yl)acetamide. 35-70. (canceled)
 71. A method of (a) treating cancer, (b) inhibiting indoleamine 2,3-dioxygenase 1 (IDO1) and/or tryptophan 2,3-dioxygenase (TDO), or (c) treating a condition or disorder selected from the group consisting of: an inflammatory condition, an infectious disease, a central nervous system disease or disorder, coronary heart disease, chronic renal failure, post anaesthesia cognitive dysfunction, a condition or disorder relating to female reproductive health, and cataracts in a warm blooded animal, including a human, comprising administering to the animal a therapeutically effective amount of a compound of Formula I, as defined in claim 1, or a pharmaceutically acceptable salt thereof. 72-80. (canceled) 